diff --git a/CHANGELOG.md b/CHANGELOG.md
index 584562e14..4daa473a4 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
    + The selected columns in the embedded resources are aggregated into arrays
    + Aggregates are not supported
  - #2967, Add `Proxy-Status` header for better error response - @taimoorzaeem
+ - #4016, Add `Content-Length` response header - @laurenceisla
 
 ### Fixed
 
diff --git a/docs/references/observability.rst b/docs/references/observability.rst
index 2ace309b1..4ebc24852 100644
--- a/docs/references/observability.rst
+++ b/docs/references/observability.rst
@@ -15,14 +15,14 @@ Observability allows measuring a system's current state based on the data it gen
 Logs
 ====
 
-PostgREST logs basic request information to ``stdout``, including the authenticated user if available, the requesting IP address and user agent, the URL requested, and HTTP response status.
+PostgREST logs basic request information to ``stdout``, including the authenticated user if available, the requesting IP address and user agent, the URL requested, the HTTP response status and the response body size in bytes if available.
 
 With :ref:`log-level` set to ``info``, we get:
 
 .. code::
 
-   127.0.0.1 - user [26/Jul/2021:01:56:38 -0500] "GET /clients HTTP/1.1" 200 - "" "curl/7.64.0"
-   127.0.0.1 - anonymous [26/Jul/2021:01:56:48 -0500] "GET /unexistent HTTP/1.1" 404 - "" "curl/7.64.0"
+   127.0.0.1 - user [26/Jul/2021:01:56:38 -0500] "GET /clients HTTP/1.1" 200 56 "" "curl/7.64.0"
+   127.0.0.1 - anonymous [26/Jul/2021:01:56:48 -0500] "GET /unexistent HTTP/1.1" 404 162 "" "curl/7.64.0"
 
 For diagnostic information about the server itself, PostgREST logs to ``stderr``:
 
@@ -73,7 +73,7 @@ This will be logged by PostgREST:
 .. code::
 
   17/Feb/2025:17:28:15 -0500: WITH pgrst_source AS ( SELECT "public"."protected_table".* FROM "public"."protected_table"  )  SELECT null::bigint AS total_result_set, pg_catalog.count(_postgrest_t) AS page_total, coalesce(json_agg(_postgrest_t), '[]') AS body, nullif(current_setting('response.headers', true), '') AS response_headers, nullif(current_setting('response.status', true), '') AS response_status, '' AS response_inserted FROM ( SELECT * FROM pgrst_source ) _postgrest_t
-  127.0.0.1 - web_anon [17/Feb/2025:17:28:15 -0500] "GET /protected_table HTTP/1.1" 401 - "" "curl/8.7.1"
+  127.0.0.1 - web_anon [17/Feb/2025:17:28:15 -0500] "GET /protected_table HTTP/1.1" 401 99 "" "curl/8.7.1"
 
 Database Logs
 -------------
@@ -270,6 +270,27 @@ This header communicates metrics of the different phases in the request-response
 
   We're working on lowering the duration of the ``parse`` and ``plan`` stages on https://github.com/PostgREST/postgrest/issues/2816.
 
+.. _content-length_header:
+
+Content-Length Header
+---------------------
+
+You can verify the response body size in bytes in the `Content-Length header <https://httpwg.org/specs/rfc9110.html#field.content-length>`_.
+
+.. code-block:: bash
+
+  curl -i 'localhost:3000/users'
+
+.. code-block:: http
+
+  HTTP/1.1 200 OK
+  Content-Length: 104
+
+Note that this header won't be returned on ``HEAD`` requests for optimization purposes (see :ref:`head_req`).
+This is in line with `RFC 9110 <https://httpwg.org/specs/rfc9110.html#field.content-length>`_.
+
+The body size is also present in the :ref:`PostgREST logs <pgrst_logging>`.
+
 .. _explain_plan:
 
 Execution plan
diff --git a/src/PostgREST/Error.hs b/src/PostgREST/Error.hs
index abc1b0e4d..9335032c4 100644
--- a/src/PostgREST/Error.hs
+++ b/src/PostgREST/Error.hs
@@ -20,6 +20,7 @@ module PostgREST.Error
 
 import qualified Data.Aeson                as JSON
 import qualified Data.ByteString.Char8     as BS
+import qualified Data.ByteString.Lazy      as LBS
 import qualified Data.CaseInsensitive      as CI
 import qualified Data.FuzzySet             as Fuzzy
 import qualified Data.HashMap.Strict       as HM
@@ -59,8 +60,11 @@ class (ErrorBody a, JSON.ToJSON a) => PgrstError a where
 
   errorResponseFor :: a -> Response
   errorResponseFor err =
-    let baseHeader = MediaType.toContentType MTApplicationJSON in
-    responseLBS (status err) (baseHeader : headers err) $ errorPayload err
+    let
+      baseHeader = MediaType.toContentType MTApplicationJSON
+      cLHeader body = (,) "Content-Length" (show $ LBS.length body) :: Header
+    in
+    responseLBS (status err) (baseHeader : cLHeader (errorPayload err) : headers err) $ errorPayload err
 
 class ErrorBody a where
   code    :: a -> Text
diff --git a/src/PostgREST/Response.hs b/src/PostgREST/Response.hs
index 0d5955368..f374a60ae 100644
--- a/src/PostgREST/Response.hs
+++ b/src/PostgREST/Response.hs
@@ -68,6 +68,7 @@ actionResponse (DbCrudResult WrappedReadPlan{wrMedia, wrHdrsOnly=headersOnly, cr
     RSStandard{..} -> do
       let
         (status, contentRange) = RangeQuery.rangeStatusHeader iTopLevelRange rsQueryTotal rsTableTotal
+        cLHeader = if headersOnly then mempty else [contentLengthHeaderStrict rsBody]
         prefHeader = maybeToList . prefAppliedHeader $ Preferences Nothing Nothing preferCount preferTransaction Nothing preferHandling preferTimezone Nothing []
         headers =
           [ contentRange
@@ -77,6 +78,7 @@ actionResponse (DbCrudResult WrappedReadPlan{wrMedia, wrHdrsOnly=headersOnly, cr
                 <> if BS.null (qsCanonical iQueryParams) then mempty else "?" <> qsCanonical iQueryParams
             )
           ]
+          ++ cLHeader
           ++ contentTypeHeaders wrMedia ctxApiRequest
           ++ prefHeader
 
@@ -90,7 +92,7 @@ actionResponse (DbCrudResult WrappedReadPlan{wrMedia, wrHdrsOnly=headersOnly, cr
       Right $ PgrstResponse ovStatus ovHeaders bod
 
     RSPlan plan ->
-      Right $ PgrstResponse HTTP.status200 (contentTypeHeaders wrMedia ctxApiRequest) $ LBS.fromStrict plan
+      Right $ PgrstResponse HTTP.status200 (contentLengthHeaderStrict plan : contentTypeHeaders wrMedia ctxApiRequest) $ LBS.fromStrict plan
 
 actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationCreate, mrMutatePlan, mrMedia, crudQi=QualifiedIdentifier{..}} resultSet) ctxApiRequest@ApiRequest{iPreferences=Preferences{..}, ..} _ _ _ _ _ = case resultSet of
   RSStandard{..} -> do
@@ -112,6 +114,7 @@ actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationCreate, mrMutateP
                 )
           , Just . RangeQuery.contentRangeH 1 0 $
               if shouldCount preferCount then Just rsQueryTotal else Nothing
+          , Just $ contentLengthHeaderStrict rsBody
           , prefHeader ]
 
     let isInsertIfGTZero i =
@@ -130,7 +133,7 @@ actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationCreate, mrMutateP
 
     Right $ PgrstResponse ovStatus ovHeaders bod
   RSPlan plan ->
-    Right $ PgrstResponse HTTP.status200 (contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
+    Right $ PgrstResponse HTTP.status200 (contentLengthHeaderStrict plan : contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
 
 actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationUpdate, mrMedia} resultSet) ctxApiRequest@ApiRequest{iPreferences=Preferences{..}} _ _ _ _ _ = case resultSet of
   RSStandard{..} -> do
@@ -143,7 +146,7 @@ actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationUpdate, mrMedia}
 
     let (status, headers', body) =
           case preferRepresentation of
-            Just Full -> (HTTP.status200, headers ++ contentTypeHeaders mrMedia ctxApiRequest, LBS.fromStrict rsBody)
+            Just Full -> (HTTP.status200, headers ++ [contentLengthHeaderStrict rsBody] ++ contentTypeHeaders mrMedia ctxApiRequest, LBS.fromStrict rsBody)
             Just None -> (HTTP.status204, headers, mempty)
             _         -> (HTTP.status204, headers, mempty)
 
@@ -152,19 +155,20 @@ actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationUpdate, mrMedia}
     Right $ PgrstResponse ovStatus ovHeaders body
 
   RSPlan plan ->
-    Right $ PgrstResponse HTTP.status200 (contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
+    Right $ PgrstResponse HTTP.status200 (contentLengthHeaderStrict plan : contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
 
 actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationSingleUpsert, mrMedia} resultSet) ctxApiRequest@ApiRequest{iPreferences=Preferences{..}} _ _ _ _ _ = case resultSet of
   RSStandard {..} -> do
     let
       prefHeader = maybeToList . prefAppliedHeader $ Preferences Nothing preferRepresentation preferCount preferTransaction Nothing preferHandling preferTimezone Nothing []
+      cLHeader = [contentLengthHeaderStrict rsBody]
       cTHeader = contentTypeHeaders mrMedia ctxApiRequest
 
     let isInsertIfGTZero i = if i > 0 then HTTP.status201 else HTTP.status200
         upsertStatus       = isInsertIfGTZero $ fromJust rsInserted
         (status, headers, body) =
           case preferRepresentation of
-            Just Full -> (upsertStatus, cTHeader ++ prefHeader, LBS.fromStrict rsBody)
+            Just Full -> (upsertStatus, cLHeader ++ cTHeader ++ prefHeader, LBS.fromStrict rsBody)
             Just None -> (HTTP.status204,  prefHeader, mempty)
             _ -> (HTTP.status204, prefHeader, mempty)
     (ovStatus, ovHeaders) <- overrideStatusHeaders rsGucStatus rsGucHeaders status headers
@@ -172,7 +176,7 @@ actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationSingleUpsert, mrM
     Right $ PgrstResponse ovStatus ovHeaders body
 
   RSPlan plan ->
-    Right $ PgrstResponse HTTP.status200 (contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
+    Right $ PgrstResponse HTTP.status200 (contentLengthHeaderStrict plan : contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
 
 actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationDelete, mrMedia} resultSet) ctxApiRequest@ApiRequest{iPreferences=Preferences{..}} _ _ _ _ _ = case resultSet of
   RSStandard {..} -> do
@@ -185,7 +189,7 @@ actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationDelete, mrMedia}
 
     let (status, headers', body) =
           case preferRepresentation of
-              Just Full -> (HTTP.status200, headers ++ contentTypeHeaders mrMedia ctxApiRequest, LBS.fromStrict rsBody)
+              Just Full -> (HTTP.status200, headers ++ [contentLengthHeaderStrict rsBody] ++ contentTypeHeaders mrMedia ctxApiRequest, LBS.fromStrict rsBody)
               Just None -> (HTTP.status204, headers, mempty)
               _ -> (HTTP.status204, headers, mempty)
 
@@ -194,7 +198,7 @@ actionResponse (DbCrudResult MutateReadPlan{mrMutation=MutationDelete, mrMedia}
     Right $ PgrstResponse ovStatus ovHeaders body
 
   RSPlan plan ->
-    Right $ PgrstResponse HTTP.status200 (contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
+    Right $ PgrstResponse HTTP.status200 (contentLengthHeaderStrict plan : contentTypeHeaders mrMedia ctxApiRequest) $ LBS.fromStrict plan
 
 actionResponse (DbCallResult CallReadPlan{crMedia, crInvMthd=invMethod, crProc=proc} resultSet) ctxApiRequest@ApiRequest{iPreferences=Preferences{..},..} _ _ _ _ _ = case resultSet of
   RSStandard {..} -> do
@@ -205,7 +209,9 @@ actionResponse (DbCallResult CallReadPlan{crMedia, crInvMthd=invMethod, crProc=p
         then Error.errorPayload $ Error.ApiRequestError $ Error.InvalidRange
           $ Error.OutOfBounds (show $ RangeQuery.rangeOffset iTopLevelRange) (maybe "0" show rsTableTotal)
         else LBS.fromStrict rsBody
+      isHeadMethod = invMethod == InvRead True
       prefHeader = maybeToList . prefAppliedHeader $ Preferences Nothing Nothing preferCount preferTransaction Nothing preferHandling preferTimezone preferMaxAffected []
+      cLHeader = if isHeadMethod then mempty else [contentLengthHeaderLazy rsOrErrBody]
       headers = contentRange : prefHeader
 
     let (status', headers', body) =
@@ -213,20 +219,22 @@ actionResponse (DbCallResult CallReadPlan{crMedia, crInvMthd=invMethod, crProc=p
               (HTTP.status204, headers, mempty)
             else
               (status,
-                headers ++ contentTypeHeaders crMedia ctxApiRequest,
-                if invMethod == InvRead True then mempty else rsOrErrBody)
+                headers ++ cLHeader ++ contentTypeHeaders crMedia ctxApiRequest,
+                if isHeadMethod then mempty else rsOrErrBody)
 
     (ovStatus, ovHeaders) <- overrideStatusHeaders rsGucStatus rsGucHeaders status' headers'
 
     Right $ PgrstResponse ovStatus ovHeaders body
 
   RSPlan plan ->
-    Right $ PgrstResponse HTTP.status200 (contentTypeHeaders crMedia ctxApiRequest) $ LBS.fromStrict plan
+    Right $ PgrstResponse HTTP.status200 (contentLengthHeaderStrict plan : contentTypeHeaders crMedia ctxApiRequest) $ LBS.fromStrict plan
 
 actionResponse (MaybeDbResult InspectPlan{ipHdrsOnly=headersOnly} body) _ versions conf sCache schema negotiatedByProfile =
-  Right $ PgrstResponse HTTP.status200
-    (MediaType.toContentType MTOpenAPI : maybeToList (profileHeader schema negotiatedByProfile))
-    (maybe mempty (\(x, y, z) -> if headersOnly then mempty else OpenAPI.encode versions conf sCache x y z) body)
+  let
+    rsBody = maybe mempty (\(x, y, z) -> if headersOnly then mempty else OpenAPI.encode versions conf sCache x y z) body
+    cLHeader = if headersOnly then mempty else [contentLengthHeaderLazy rsBody]
+  in
+  Right $ PgrstResponse HTTP.status200 (MediaType.toContentType MTOpenAPI : cLHeader ++ maybeToList (profileHeader schema negotiatedByProfile)) rsBody
 
 actionResponse (NoDbResult (RelInfoPlan qi@QualifiedIdentifier{..})) _ _ _ SchemaCache{dbTables} _ _ =
   case HM.lookup qi dbTables of
@@ -251,7 +259,7 @@ actionResponse (NoDbResult SchemaInfoPlan) _ _ _ _ _ _ = respondInfo "OPTIONS,GE
 respondInfo :: ByteString -> Either Error.Error PgrstResponse
 respondInfo allowHeader =
   let allOrigins = ("Access-Control-Allow-Origin", "*") in
-  Right $ PgrstResponse HTTP.status200 [allOrigins, (HTTP.hAllow, allowHeader)] mempty
+  Right $ PgrstResponse HTTP.status200 [contentLengthHeaderStrict mempty, allOrigins, (HTTP.hAllow, allowHeader)] mempty
 
 -- Status and headers can be overridden as per https://postgrest.org/en/stable/references/transactions.html#response-headers
 overrideStatusHeaders :: Maybe Text -> Maybe BS.ByteString -> HTTP.Status -> [HTTP.Header]-> Either Error.Error (HTTP.Status, [HTTP.Header])
@@ -268,6 +276,15 @@ decodeGucStatus :: Maybe Text -> Either Error.Error (Maybe HTTP.Status)
 decodeGucStatus =
   maybe (Right Nothing) $ first (const . Error.ApiRequestError $ Error.GucStatusError) . fmap (Just . toEnum . fst) . decimal
 
+contentLengthHeader :: Show b => (a -> b) -> a -> HTTP.Header
+contentLengthHeader lenFn body = ("Content-Length", show (lenFn body))
+
+contentLengthHeaderStrict :: BS.ByteString -> HTTP.Header
+contentLengthHeaderStrict = contentLengthHeader BS.length
+
+contentLengthHeaderLazy :: LBS.ByteString -> HTTP.Header
+contentLengthHeaderLazy = contentLengthHeader LBS.length
+
 contentTypeHeaders :: MediaType -> ApiRequest -> [HTTP.Header]
 contentTypeHeaders mediaType ApiRequest{..} =
   MediaType.toContentType mediaType : maybeToList (profileHeader iSchema iNegotiatedByProfile)
diff --git a/test/io/test_io.py b/test/io/test_io.py
index 02d31349c..72c2ff892 100644
--- a/test/io/test_io.py
+++ b/test/io/test_io.py
@@ -964,45 +964,45 @@ def test_log_level(level, defaultenv):
             assert len(output) == 0
         elif level == "error":
             assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 - "" "python-requests/.+"',
+                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
                 output[0],
             )
             assert len(output) == 1
         elif level == "warn":
             assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 - "" "python-requests/.+"',
+                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
                 output[0],
             )
             assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 - "" "python-requests/.+"',
+                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
                 output[1],
             )
             assert len(output) == 2
         elif level == "info":
             assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 - "" "python-requests/.+"',
+                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
                 output[0],
             )
             assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 - "" "python-requests/.+"',
+                r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 \d+ "" "python-requests/.+"',
                 output[1],
             )
             assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 - "" "python-requests/.+"',
+                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
                 output[2],
             )
             assert len(output) == 3
         elif level == "debug":
             assert re.match(
-                r'- - - \[.+\] "GET / HTTP/1.1" 500 - "" "python-requests/.+"',
+                r'- - - \[.+\] "GET / HTTP/1.1" 500 \d+ "" "python-requests/.+"',
                 output[0],
             )
             assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 - "" "python-requests/.+"',
+                r'- - postgrest_test_anonymous \[.+\] "GET / HTTP/1.1" 200 \d+ "" "python-requests/.+"',
                 output[1],
             )
             assert re.match(
-                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 - "" "python-requests/.+"',
+                r'- - postgrest_test_anonymous \[.+\] "GET /unknown HTTP/1.1" 404 \d+ "" "python-requests/.+"',
                 output[2],
             )
 
diff --git a/test/spec/Feature/Auth/AuthSpec.hs b/test/spec/Feature/Auth/AuthSpec.hs
index cb91a2bd1..f30f7aa4b 100644
--- a/test/spec/Feature/Auth/AuthSpec.hs
+++ b/test/spec/Feature/Auth/AuthSpec.hs
@@ -22,7 +22,8 @@ spec = describe "authorization" $ do
         "code":"42501",
         "message":"permission denied for table authors_only"} |]
       { matchStatus = 401
-      , matchHeaders = ["WWW-Authenticate" <:> "Bearer"]
+      , matchHeaders = [ "WWW-Authenticate" <:> "Bearer"
+                       , "Content-Length" <:> "96" ]
       }
 
   it "denies access to tables that postgrest_test_author does not own" $
@@ -35,7 +36,7 @@ spec = describe "authorization" $ do
         "code":"42501",
         "message":"permission denied for table private_table"} |]
       { matchStatus = 403
-      , matchHeaders = []
+      , matchHeaders = ["Content-Length" <:> "97"]
       }
 
   it "denies execution on functions that anonymous does not own" $
@@ -92,7 +93,8 @@ spec = describe "authorization" $ do
       { matchStatus = 401
       , matchHeaders = [
           "WWW-Authenticate" <:>
-          "Bearer error=\"invalid_token\", error_description=\"Empty JWT is sent in Authorization header\""
+          "Bearer error=\"invalid_token\", error_description=\"Empty JWT is sent in Authorization header\"",
+          "Content-Length" <:> "100"
         ]
       }
 
diff --git a/test/spec/Feature/OpenApi/DisabledOpenApiSpec.hs b/test/spec/Feature/OpenApi/DisabledOpenApiSpec.hs
index 75ececd76..ce322da07 100644
--- a/test/spec/Feature/OpenApi/DisabledOpenApiSpec.hs
+++ b/test/spec/Feature/OpenApi/DisabledOpenApiSpec.hs
@@ -17,4 +17,5 @@ spec =
         [("Accept","application/openapi+json")] ""
         `shouldRespondWith`
         [json| {"code":"PGRST126","details":null,"hint":null,"message":"Root endpoint metadata is disabled"} |]
-        { matchStatus = 404 }
+        { matchStatus = 404
+        , matchHeaders = ["Content-Length" <:> "93"]}
diff --git a/test/spec/Feature/OpenApi/IgnorePrivOpenApiSpec.hs b/test/spec/Feature/OpenApi/IgnorePrivOpenApiSpec.hs
index f943268f4..00310b187 100644
--- a/test/spec/Feature/OpenApi/IgnorePrivOpenApiSpec.hs
+++ b/test/spec/Feature/OpenApi/IgnorePrivOpenApiSpec.hs
@@ -25,7 +25,8 @@ spec = describe "OpenAPI Ignore Privileges" $ do
       `shouldRespondWith`
         ""
         { matchStatus  = 200
-        , matchHeaders = [ "Content-Type" <:> "application/openapi+json; charset=utf-8" ]
+        , matchHeaders = [ "Content-Type" <:> "application/openapi+json; charset=utf-8"
+                         , matchHeaderAbsent hContentLength]
         }
 
   describe "table" $ do
diff --git a/test/spec/Feature/OpenApi/OpenApiSpec.hs b/test/spec/Feature/OpenApi/OpenApiSpec.hs
index d17b7427f..fbe227a32 100644
--- a/test/spec/Feature/OpenApi/OpenApiSpec.hs
+++ b/test/spec/Feature/OpenApi/OpenApiSpec.hs
@@ -24,7 +24,8 @@ spec = describe "OpenAPI" $ do
       `shouldRespondWith`
         ""
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "application/openapi+json; charset=utf-8"]
+        , matchHeaders = [ "Content-Type" <:> "application/openapi+json; charset=utf-8"
+                         , matchHeaderAbsent hContentLength ]
         }
 
   it "should respond to openapi request on none root path with 406" $
@@ -38,11 +39,14 @@ spec = describe "OpenAPI" $ do
       `shouldRespondWith` 406
 
   it "includes postgrest.org current version api docs" $ do
-    r <- simpleBody <$> get "/"
+    r <- get "/"
 
-    let docsUrl = r ^? key "externalDocs" . key "url"
+    let headers = simpleHeaders r
+        docsUrl = simpleBody r ^? key "externalDocs" . key "url"
 
-    liftIO $ docsUrl `shouldBe` Just (String ("https://postgrest.org/en/" <> docsVersion <> "/references/api.html"))
+    liftIO $ do
+      headers `shouldSatisfy` notZeroContentLength
+      docsUrl `shouldBe` Just (String ("https://postgrest.org/en/" <> docsVersion <> "/references/api.html"))
 
   describe "schema" $ do
 
diff --git a/test/spec/Feature/OptionsSpec.hs b/test/spec/Feature/OptionsSpec.hs
index e5aa54ab9..44e898fdd 100644
--- a/test/spec/Feature/OptionsSpec.hs
+++ b/test/spec/Feature/OptionsSpec.hs
@@ -15,9 +15,9 @@ spec = describe "Allow header" $ do
   context "a table" $ do
     it "includes read/write methods for writeable table" $ do
       r <- request methodOptions "/items" [] ""
-      liftIO $
-        simpleHeaders r `shouldSatisfy`
-          matchHeader "Allow" "OPTIONS,GET,HEAD,POST,PUT,PATCH,DELETE"
+      liftIO $ do
+        simpleHeaders r `shouldSatisfy` matchHeader "Allow" "OPTIONS,GET,HEAD,POST,PUT,PATCH,DELETE"
+        simpleHeaders r `shouldSatisfy` matchHeader "Content-Length" "0"
 
     it "fails with 404 for an unknown table" $
       request methodOptions "/unknown" [] "" `shouldRespondWith` 404
diff --git a/test/spec/Feature/Query/CustomMediaSpec.hs b/test/spec/Feature/Query/CustomMediaSpec.hs
index 1459c55ab..e20b6da67 100644
--- a/test/spec/Feature/Query/CustomMediaSpec.hs
+++ b/test/spec/Feature/Query/CustomMediaSpec.hs
@@ -20,6 +20,7 @@ spec = describe "custom media types" $ do
       liftIO $ do
         simpleBody r `shouldBe` readFixtureFile "lines.twkb"
         simpleHeaders r `shouldContain` [("Content-Type", "application/vnd.twkb")]
+        simpleHeaders r `shouldContain` [("Content-Length", "30")]
 
     it "can query by id if there's an aggregate defined for the table" $ do
       r <- request methodGet "/lines?id=eq.1" (acceptHdrs "application/vnd.twkb") ""
@@ -32,7 +33,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         [json| {"code":"PGRST107","details":null,"hint":null,"message":"None of these media types are available: text/plain"} |]
         { matchStatus  = 406
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [ matchContentTypeJson
+                         , "Content-Length" <:> "110" ]
         }
 
     it "can get raw xml output with Accept: text/xml if there's an aggregate defined" $ do
@@ -40,7 +42,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         "<myxml>foo</myxml>bar<foobar><baz/></foobar>"
         { matchStatus = 200
-        , matchHeaders = ["Content-Type" <:> "text/xml; charset=utf-8"]
+        , matchHeaders = [ "Content-Type" <:> "text/xml; charset=utf-8"
+                         , "Content-Length" <:> "44"]
         }
 
   -- TODO SOH (start of heading) is being added to results
@@ -50,7 +53,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         "\SOH{\"type\": \"FeatureCollection\", \"hello\": \"world\"}"
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "application/vnd.geo2+json"]
+        , matchHeaders = [ "Content-Type" <:> "application/vnd.geo2+json"
+                         , "Content-Length" <:> "48" ]
         }
 
     it "will use the more specific application/vnd.geo2 handler for this table" $ do
@@ -83,14 +87,16 @@ spec = describe "custom media types" $ do
             |</html>
             |]
         { matchStatus = 200
-        , matchHeaders = ["Content-Type" <:> "text/html"]
+        , matchHeaders = [ "Content-Type" <:> "text/html"
+                         , "Content-Length" <:> "117" ]
         }
 
     it "can get raw output with Accept: text/plain" $ do
       request methodGet "/rpc/welcome" (acceptHdrs "text/plain") ""
         `shouldRespondWith` "Welcome to PostgREST"
         { matchStatus = 200
-        , matchHeaders = ["Content-Type" <:> "text/plain; charset=utf-8"]
+        , matchHeaders = [ "Content-Type" <:> "text/plain; charset=utf-8"
+                         , "Content-Length" <:> "20" ]
         }
 
     it "can get raw xml output with Accept: text/xml" $ do
@@ -98,7 +104,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         "<my-xml-tag/>"
         { matchStatus = 200
-        , matchHeaders = ["Content-Type" <:> "text/xml; charset=utf-8"]
+        , matchHeaders = [ "Content-Type" <:> "text/xml; charset=utf-8"
+                         , "Content-Length" <:> "13" ]
         }
 
     it "can get raw xml output with Accept: text/xml" $ do
@@ -132,6 +139,7 @@ spec = describe "custom media types" $ do
       liftIO $ do
         simpleBody r `shouldBe` readFixtureFile "A.png"
         simpleHeaders r `shouldContain` [("Content-Type", "image/png")]
+        simpleHeaders r `shouldContain` [("Content-Length", "138")]
 
   context "Proc that returns set of scalars and Accept: text/plain" $
     it "will err because only scalars work with media type domains" $ do
@@ -141,7 +149,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
           [json|{"code":"PGRST107","details":null,"hint":null,"message":"None of these media types are available: text/plain"}|]
           { matchStatus = 406
-          , matchHeaders = ["Content-Type" <:> "application/json; charset=utf-8"]
+          , matchHeaders = [ "Content-Type" <:> "application/json; charset=utf-8"
+                           , "Content-Length" <:> "110"]
           }
 
   context "Proc that returns rows and accepts custom media type" $ do
@@ -173,7 +182,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         [json| {"overridden": "true"} |]
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "application/json; charset=utf-8"]
+        , matchHeaders = [ "Content-Type" <:> "application/json; charset=utf-8"
+                         , "Content-Length" <:> "22" ]
         }
 
     -- TODO SOH (start of heading) is being added to results
@@ -182,7 +192,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         "\SOH{\"crs\": {\"type\": \"name\", \"properties\": {\"name\": \"EPSG:4326\"}}, \"type\": \"FeatureCollection\", \"features\": [{\"type\": \"Feature\", \"geometry\": {\"type\": \"LineString\", \"coordinates\": [[1, 1], [5, 5]]}, \"properties\": {\"id\": 1, \"name\": \"line-1\"}}]}"
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "application/geo+json; charset=utf-8"]
+        , matchHeaders = [ "Content-Type" <:> "application/geo+json; charset=utf-8"
+                         , "Content-Length" <:> "239" ]
         }
 
     it "will not override vendored media types like application/vnd.pgrst.object" $
@@ -190,7 +201,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         [json|{"id":1,"name":"Windows 7","client_id":1}|]
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "application/vnd.pgrst.object+json; charset=utf-8"]
+        , matchHeaders = [ "Content-Type" <:> "application/vnd.pgrst.object+json; charset=utf-8"
+                         , "Content-Length" <:> "41" ]
         }
 
   context "matches requested media type correctly" $ do
@@ -200,11 +212,13 @@ spec = describe "custom media types" $ do
       liftIO $ do
         simpleBody r1 `shouldBe` readFixtureFile "A.png"
         simpleHeaders r1 `shouldContain` [("Content-Type", "image/png")]
+        simpleHeaders r1 `shouldContain` [("Content-Length", "138")]
 
       r2 <- request methodGet "/rpc/ret_image" (acceptHdrs "text/html,application/xhtml+xml,application/xml;q=0.9,image/png,*/*;q=0.8") ""
       liftIO $ do
         simpleBody r2 `shouldBe` readFixtureFile "A.png"
         simpleHeaders r2 `shouldContain` [("Content-Type", "image/png")]
+        simpleHeaders r2 `shouldContain` [("Content-Length", "138")]
 
     -- https://github.com/PostgREST/postgrest/issues/2170
     it "will match json in presence of text/plain" $ do
@@ -219,7 +233,8 @@ spec = describe "custom media types" $ do
         `shouldRespondWith`
         "id\tname\tclient_id\n1\tWindows 7\t1\n2\tWindows 10\t1\n"
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "text/tab-separated-values"]
+        , matchHeaders = [ "Content-Type" <:> "text/tab-separated-values"
+                         , "Content-Length" <:> "47" ]
         }
 
     -- https://github.com/PostgREST/postgrest/issues/1371#issuecomment-519248984
@@ -229,6 +244,7 @@ spec = describe "custom media types" $ do
         simpleBody r `shouldBe` readFixtureFile "lines.csv"
         simpleHeaders r `shouldContain` [("Content-Type", "text/csv; charset=utf-8")]
         simpleHeaders r `shouldContain` [("Content-Disposition", "attachment; filename=\"lines.csv\"")]
+        simpleHeaders r `shouldContain` [("Content-Length", "216")]
 
   -- https://github.com/PostgREST/postgrest/issues/3160
   context "using select query parameter" $ do
@@ -239,7 +255,8 @@ spec = describe "custom media types" $ do
             |(2,"Windows 10",1)
             |]
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "pg/outfunc"]
+        , matchHeaders = [ "Content-Type" <:> "pg/outfunc"
+                         , "Content-Length" <:> "37" ]
         }
 
     it "with fewer columns selected" $ do
diff --git a/test/spec/Feature/Query/DeleteSpec.hs b/test/spec/Feature/Query/DeleteSpec.hs
index 486446643..5a3d18928 100644
--- a/test/spec/Feature/Query/DeleteSpec.hs
+++ b/test/spec/Feature/Query/DeleteSpec.hs
@@ -22,6 +22,7 @@ spec =
             ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "*/*" ]
             }
 
@@ -30,6 +31,7 @@ spec =
           `shouldRespondWith` [json|[{"id":2}]|]
           { matchStatus  = 200
           , matchHeaders = ["Content-Range" <:> "*/1"
+                           , "Content-Length" <:> "10"
                            , "Preference-Applied" <:> "return=representation, count=exact"]
           }
 
@@ -41,6 +43,7 @@ spec =
             ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "*/*" ]
             }
         request methodDelete "/items?id=eq.3&select=id"
@@ -50,6 +53,7 @@ spec =
             ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "*/*"
                              , "Preference-Applied" <:> "return=minimal"]
             }
@@ -58,7 +62,8 @@ spec =
         request methodDelete "/complex_items?id=eq.2&select=id,name" [("Prefer", "return=representation")] ""
           `shouldRespondWith` [json|[{"id":2,"name":"Two"}]|]
           { matchStatus  = 200
-          , matchHeaders = ["Content-Range" <:> "*/*"]
+          , matchHeaders = [ "Content-Range" <:> "*/*"
+                           , "Content-Length" <:> "23" ]
           }
 
       it "can rename and cast the selected columns" $
@@ -137,6 +142,7 @@ spec =
             ""
             { matchStatus = 204
             , matchHeaders = [matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Preference-Applied" <:> "return=minimal" ]
             }
 
@@ -147,7 +153,8 @@ spec =
           `shouldRespondWith`
             ""
             { matchStatus = 204
-            , matchHeaders = [matchHeaderAbsent hContentType]
+            , matchHeaders = [matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength]
             }
 
     context "with ordering" $
diff --git a/test/spec/Feature/Query/EmbedDisambiguationSpec.hs b/test/spec/Feature/Query/EmbedDisambiguationSpec.hs
index d99903d1c..48bf08197 100644
--- a/test/spec/Feature/Query/EmbedDisambiguationSpec.hs
+++ b/test/spec/Feature/Query/EmbedDisambiguationSpec.hs
@@ -40,7 +40,8 @@ spec =
             }
           |]
           { matchStatus  = 300
-          , matchHeaders = [matchContentTypeJson]
+          , matchHeaders = [ matchContentTypeJson
+                           , "Content-Length" <:> "828" ]
           }
 
       it "errs on an ambiguous embed that has a circular reference" $
diff --git a/test/spec/Feature/Query/ErrorSpec.hs b/test/spec/Feature/Query/ErrorSpec.hs
index 0f207746f..1c7bb3e20 100644
--- a/test/spec/Feature/Query/ErrorSpec.hs
+++ b/test/spec/Feature/Query/ErrorSpec.hs
@@ -26,7 +26,8 @@ pgErrorCodeMapping = do
            "details": null,
            "hint": "Increase the configuration parameter \"max_stack_depth\" (currently 2048kB), after ensuring the platform's stack depth limit is adequate.",
             "message": "stack depth limit exceeded"}|]
-        { matchStatus = 500 }
+        { matchStatus = 500
+        , matchHeaders = ["Content-Length" <:> "217"] }
 
     context "includes the proxy-status header on the response" $ do
       it "works with ApiRequest error" $
@@ -34,7 +35,8 @@ pgErrorCodeMapping = do
           `shouldRespondWith`
           [json| {"code":"PGRST125","details":null,"hint":null,"message":"Invalid path specified in request URL"} |]
           { matchStatus  = 404
-          , matchHeaders = ["Proxy-Status" <:> "PostgREST; error=PGRST125"]
+          , matchHeaders = [ "Proxy-Status" <:> "PostgREST; error=PGRST125"
+                           , "Content-Length" <:> "96" ]
           }
 
       it "works with SchemaCache error" $
@@ -42,7 +44,8 @@ pgErrorCodeMapping = do
           `shouldRespondWith`
           [json| {"code":"PGRST205","details":null,"hint":"Perhaps you meant the table 'test.json_table'","message":"Could not find the table 'test.non_existent_table' in the schema cache"} |]
           { matchStatus  = 404
-          , matchHeaders = ["Proxy-Status" <:> "PostgREST; error=PGRST205"]
+          , matchHeaders = [ "Proxy-Status" <:> "PostgREST; error=PGRST205"
+                           , "Content-Length" <:> "172" ]
           }
 
       it "works with Jwt error" $ do
@@ -51,7 +54,8 @@ pgErrorCodeMapping = do
           `shouldRespondWith`
           [json| {"message":"Expected 3 parts in JWT; got 2","code":"PGRST301","hint":null,"details":null} |]
           { matchStatus = 401
-          , matchHeaders = ["Proxy-Status" <:> "PostgREST; error=PGRST301"]
+          , matchHeaders = [ "Proxy-Status" <:> "PostgREST; error=PGRST301"
+                           , "Content-Length" <:> "89" ]
           }
 
       it "works with raise sqlstate custom error" $
@@ -59,7 +63,8 @@ pgErrorCodeMapping = do
           `shouldRespondWith`
           [json| {"code":"PT402","details":"Quota exceeded","hint":"Upgrade your plan","message":"Payment Required"} |]
           { matchStatus  = 402
-          , matchHeaders = ["Proxy-Status" <:> "PostgREST; error=PT402"]
+          , matchHeaders = [ "Proxy-Status" <:> "PostgREST; error=PT402"
+                           , "Content-Length" <:> "99" ]
           }
 
       it "works with sqlstate PGRST custom error" $
@@ -67,5 +72,6 @@ pgErrorCodeMapping = do
           `shouldRespondWith`
           [json| {"code":"123","details":"DEF","hint":"XYZ","message":"ABC"} |]
           { matchStatus  = 332
-          , matchHeaders = ["Proxy-Status" <:> "PostgREST; error=123"]
+          , matchHeaders = [ "Proxy-Status" <:> "PostgREST; error=123"
+                           , "Content-Length" <:> "59" ]
           }
diff --git a/test/spec/Feature/Query/InsertSpec.hs b/test/spec/Feature/Query/InsertSpec.hs
index 6d070ca03..b016333a4 100644
--- a/test/spec/Feature/Query/InsertSpec.hs
+++ b/test/spec/Feature/Query/InsertSpec.hs
@@ -30,7 +30,8 @@ spec actualPgVersion = do
           } |] `shouldRespondWith` ""
           { matchStatus  = 201
             -- should not have content type set when body is empty
-          , matchHeaders = [matchHeaderAbsent hContentType]
+          , matchHeaders = [ matchHeaderAbsent hContentType
+                           , "Content-Length" <:> "0"]
           }
 
       it "filters columns in result using &select" $
@@ -42,6 +43,7 @@ spec actualPgVersion = do
           }] |] `shouldRespondWith` [json|[{"integer":14,"varchar":"testing!"}]|]
           { matchStatus  = 201
           , matchHeaders = [matchContentTypeJson
+                           , "Content-Length" <:> "37"
                            , "Preference-Applied" <:> "return=representation"]
           }
 
@@ -187,7 +189,8 @@ spec actualPgVersion = do
             `shouldRespondWith`
               ""
               { matchStatus = 204
-              , matchHeaders = [ matchHeaderAbsent hContentType ]
+              , matchHeaders = [  matchHeaderAbsent hContentType
+                                , matchHeaderAbsent hContentLength ]
               }
 
           request methodPost "/auto_incrementing_pk"
@@ -211,7 +214,7 @@ spec actualPgVersion = do
             [json|{"hint":null,"details":"Failing row contains (null, foo).","code":"23502","message":"null value in column \"k\" violates not-null constraint"}|]
           )
           { matchStatus  = 400
-          , matchHeaders = [matchContentTypeJson]
+          , matchHeaders = [ matchContentTypeJson]
           }
 
       context "into a table with no pk" $ do
@@ -286,7 +289,8 @@ spec actualPgVersion = do
         `shouldRespondWith`
         [json|{"message":"Empty or invalid json","code":"PGRST102","details":null,"hint":null}|]
         { matchStatus  = 400
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [ matchContentTypeJson,
+                           "Content-Length" <:> "80" ]
         }
 
     context "with no payload" $
@@ -370,7 +374,8 @@ spec actualPgVersion = do
           `shouldRespondWith`
             ""
             { matchStatus = 204
-            , matchHeaders = [ matchHeaderAbsent hContentType ]
+            , matchHeaders = [  matchHeaderAbsent hContentType
+                              , matchHeaderAbsent hContentLength ]
             }
 
         request methodPost "/items2"
@@ -388,7 +393,8 @@ spec actualPgVersion = do
           `shouldRespondWith`
             ""
             { matchStatus = 204
-            , matchHeaders = [ matchHeaderAbsent hContentType ]
+            , matchHeaders = [  matchHeaderAbsent hContentType
+                              , matchHeaderAbsent hContentLength ]
             }
 
         request methodPost "/items3?select=id"
@@ -623,7 +629,8 @@ spec actualPgVersion = do
           `shouldRespondWith`
             ""
             { matchStatus = 204
-            , matchHeaders = [matchHeaderAbsent hContentType]
+            , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength ]
             }
 
   describe "CSV insert" $ do
diff --git a/test/spec/Feature/Query/PlanSpec.hs b/test/spec/Feature/Query/PlanSpec.hs
index 837332b21..c27e2b597 100644
--- a/test/spec/Feature/Query/PlanSpec.hs
+++ b/test/spec/Feature/Query/PlanSpec.hs
@@ -33,6 +33,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         totalCost `shouldBe` (if actualPgVersion >= pgVersion170 then 11.32 else 15.63)
 
@@ -140,6 +141,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         totalCost `shouldBe` 0.06
 
@@ -153,6 +155,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         totalCost `shouldBe` 8.23
 
@@ -166,6 +169,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         totalCost `shouldBe` (if actualPgVersion >= pgVersion170 then 11.37 else 15.68)
 
@@ -180,6 +184,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         totalCost `shouldBe` 3.55
 
@@ -194,6 +199,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         totalCost `shouldBe` 5.53
 
@@ -248,6 +254,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/vnd.pgrst.object+json\"; options=verbose; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         aggCol `shouldBe` Just [aesonQQ| "COALESCE((json_agg(ROW(projects.id, projects.name, projects.client_id)) -> 0), 'null'::json)" |]
 
   describe "function plan" $ do
@@ -261,6 +268,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+json; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         totalCost `shouldBe` 68.56
 
@@ -275,6 +283,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+text; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         resBody `shouldSatisfy` (\t -> LBS.take 9 t == "Aggregate")
 
@@ -288,6 +297,7 @@ spec actualPgVersion = do
 
       liftIO $ do
         resHeaders `shouldSatisfy` elem ("Content-Type", "application/vnd.pgrst.plan+text; for=\"application/json\"; charset=utf-8")
+        resHeaders `shouldSatisfy` notZeroContentLength
         resStatus `shouldBe` Status { statusCode = 200, statusMessage="OK" }
         resBody `shouldSatisfy` (\t -> LBS.take 9 t == "Aggregate")
 
diff --git a/test/spec/Feature/Query/QuerySpec.hs b/test/spec/Feature/Query/QuerySpec.hs
index d341ad07b..43cb46723 100644
--- a/test/spec/Feature/Query/QuerySpec.hs
+++ b/test/spec/Feature/Query/QuerySpec.hs
@@ -28,14 +28,17 @@ spec = do
       `shouldRespondWith`
       [json| {"code":"PGRST205","details":null,"hint":"Perhaps you meant the table 'test.private_table'","message":"Could not find the table 'test.faketable' in the schema cache"} |]
       { matchStatus = 404
-      , matchHeaders = []
+      , matchHeaders = ["Content-Length" <:> "166"]
       }
 
   describe "Filtering response" $ do
     it "matches with equality" $
       get "/items?id=eq.5"
         `shouldRespondWith` [json| [{"id":5}] |]
-        { matchHeaders = ["Content-Range" <:> "0-0/*"] }
+        { matchHeaders = [
+            "Content-Range" <:> "0-0/*",
+            "Content-Length" <:> "10"
+          ] }
 
     it "matches with equality using not operator" $
       get "/items?id=not.eq.5&order=id"
@@ -511,7 +514,10 @@ spec = do
            "code":"PGRST108",
            "message":"'non_existent_projects' is not an embedded resource in this request"}|]
         { matchStatus  = 400
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [
+            "Content-Length" <:> "204",
+            matchContentTypeJson
+          ]
         }
       get "/clients?select=*,amiga_projects:projects(*)&amiga_projectsss.name=ilike.*Amiga*" `shouldRespondWith`
         [json|
@@ -590,7 +596,7 @@ spec = do
       get "/complex_items?select=id::fakecolumntype"
         `shouldRespondWith` [json| {"hint":null,"details":null,"code":"42704","message":"type \"fakecolumntype\" does not exist"} |]
         { matchStatus  = 400
-        , matchHeaders = []
+        , matchHeaders = ["Content-Length" <:> "94"]
         }
 
     it "can cast types with underscore and numbers" $
@@ -603,7 +609,11 @@ spec = do
     it "requesting parents and children" $
       get "/projects?id=eq.1&select=id, name, clients(*), tasks(id, name)" `shouldRespondWith`
         [json|[{"id":1,"name":"Windows 7","clients":{"id":1,"name":"Microsoft"},"tasks":[{"id":1,"name":"Design w7"},{"id":2,"name":"Code w7"}]}]|]
-        { matchHeaders = [matchContentTypeJson] }
+        { matchHeaders = [
+            "Content-Length" <:> "141",
+            matchContentTypeJson
+          ]
+        }
 
     it "requesting parent and renaming primary key" $
       get "/projects?select=name,client:clients(clientId:id,name)" `shouldRespondWith`
@@ -1145,7 +1155,10 @@ spec = do
       get "/items?order=id.asc.nullslasttt" `shouldRespondWith`
         [json|{"details":"unexpected 't' expecting \",\" or end of input","message":"\"failed to parse order (id.asc.nullslasttt)\" (line 1, column 17)","code":"PGRST100","hint":null}|]
         { matchStatus  = 400
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [
+            "Content-Length" <:> "169",
+            matchContentTypeJson
+          ]
         }
 
   describe "Accept headers" $ do
@@ -1155,7 +1168,10 @@ spec = do
         `shouldRespondWith`
         [json|{"message":"None of these media types are available: text/unknowntype","code":"PGRST107","details":null,"hint":null}|]
         { matchStatus  = 406
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [
+            "Content-Length" <:> "116",
+            matchContentTypeJson
+          ]
         }
 
     it "should respond correctly to */* in accept header" $
@@ -1194,7 +1210,10 @@ spec = do
               (acceptHdrs "text/csv; version=1") ""
         `shouldRespondWith` "k,extra\nxyyx,u\nxYYx,v"
         { matchStatus  = 200
-        , matchHeaders = ["Content-Type" <:> "text/csv; charset=utf-8"]
+        , matchHeaders = [
+            "Content-Type" <:> "text/csv; charset=utf-8",
+            "Content-Length" <:> "21"
+          ]
         }
 
   describe "Canonical location" $ do
@@ -1512,7 +1531,10 @@ spec = do
       get "/datarep_todos?select=id,label_color,banana" `shouldRespondWith`
         [json| {"code":"42703","details":null,"hint":null,"message":"column datarep_todos.banana does not exist"} |]
         { matchStatus  = 400
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [
+            "Content-Length" <:> "98",
+            matchContentTypeJson
+          ]
         }
     it "formats columns in views including computed columns" $
       get "/datarep_todos_computed?select=id,label_color,dark_color" `shouldRespondWith`
@@ -1548,8 +1570,8 @@ spec = do
       get "/datarep_todos?id=lt.4" `shouldRespondWith`
         [json| [
           {"id":1,"name":"Report","label_color":"#000000","due_at":"2018-01-02T00:00:00Z","icon_image":"iVBORw0KGgoAAAANSUhEUgAAAAEAAAABAQAAAAA3bvkkAAAAABBJREFUeJxiYAEAAAAA//8DAAAABgAFBXv6vUAAAAAASUVORK5CYII=","created_at":1513213350,"budget":"12.50"},
- {"id":2,"name":"Essay","label_color":"#000100","due_at":"2018-01-03T00:00:00Z","icon_image":null,"created_at":1513213350,"budget":"100000000000000.13"},
- {"id":3,"name":"Algebra","label_color":"#01E240","due_at":"2018-01-01T14:12:34.123456Z","icon_image":null,"created_at":1513213350,"budget":"0.00"}
+          {"id":2,"name":"Essay","label_color":"#000100","due_at":"2018-01-03T00:00:00Z","icon_image":null,"created_at":1513213350,"budget":"100000000000000.13"},
+          {"id":3,"name":"Algebra","label_color":"#01E240","due_at":"2018-01-01T14:12:34.123456Z","icon_image":null,"created_at":1513213350,"budget":"0.00"}
         ] |]
         { matchHeaders = [matchContentTypeJson] }
     it "formats star and explicit mix" $
@@ -1580,7 +1602,10 @@ spec = do
         -- we prove the parser is not used because it'd replace the Z with `+00:00` and a different error message.
         [json| {"code":"22007","details":null,"hint":null,"message":"invalid input syntax for type timestamp with time zone: \"Z\""} |]
         { matchStatus  = 400
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [
+            "Content-Length" <:> "117",
+            matchContentTypeJson
+          ]
         }
     it "uses text parser for filter with 'IN' predicates" $
       get "/datarep_todos?select=id,due_at&label_color=in.(000100,01E240)" `shouldRespondWith`
@@ -1607,7 +1632,10 @@ spec = do
           {"code":"42883","details":null,"hint":"No operator matches the given name and argument types. You might need to add explicit type casts.","message":"operator does not exist: public.color ~~* unknown"}
         |]
         { matchStatus  = 404
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [
+            "Content-Length" <:> "200",
+            matchContentTypeJson
+          ]
         }
 
   context "searching for an empty string" $ do
@@ -1624,11 +1652,13 @@ spec = do
     it "return http status 500" $
       get "/infinite_recursion?select=*" `shouldRespondWith`
         [json|{"code":"42P17","message":"infinite recursion detected in rules for relation \"infinite_recursion\"","details":null,"hint":null}|]
-        { matchStatus = 500 }
+        { matchStatus = 500
+        , matchHeaders = ["Content-Length" <:> "128"] }
 
   context "invalid resource path" $ do
     it "return http status 404" $
       get "/first/second/third?select=*"
       `shouldRespondWith`
       [json| {"code":"PGRST125","details":null,"hint":null,"message":"Invalid path specified in request URL"} |]
-      { matchStatus = 404 }
+      { matchStatus = 404
+      , matchHeaders = ["Content-Length" <:> "96"]}
diff --git a/test/spec/Feature/Query/RangeSpec.hs b/test/spec/Feature/Query/RangeSpec.hs
index 5eb2e1774..3086be605 100644
--- a/test/spec/Feature/Query/RangeSpec.hs
+++ b/test/spec/Feature/Query/RangeSpec.hs
@@ -22,7 +22,10 @@ spec = do
       context "when I don't want the count" $ do
         it "returns range Content-Range with */* for empty range" $
           get "/rpc/getitemrange?min=2&max=2"
-            `shouldRespondWith` [json| [] |] {matchHeaders = ["Content-Range" <:> "*/*"]}
+            `shouldRespondWith` [json| [] |]
+              { matchHeaders = [ "Content-Range" <:> "*/*"
+                               , "Content-Length" <:> "2" ]
+              }
 
         it "returns range Content-Range with range/*" $
           get "/rpc/getitemrange?order=id&min=0&max=15"
@@ -42,7 +45,8 @@ spec = do
                 "hint":null
               }|]
             { matchStatus  = 416
-            , matchHeaders = ["Content-Range" <:> "*/0"]
+            , matchHeaders = [ "Content-Range" <:> "*/0"
+                             , "Content-Length" <:> "144"]
             }
 
         it "refuses a range requesting start past last item" $
@@ -65,8 +69,8 @@ spec = do
           r <- request methodGet  "/rpc/getitemrange?min=0&max=15"
                        (rangeHdrs $ ByteRangeFromTo 0 1) mempty
           liftIO $ do
-            simpleHeaders r `shouldSatisfy`
-              matchHeader "Content-Range" "0-1/*"
+            simpleHeaders r `shouldSatisfy` matchHeader "Content-Range" "0-1/*"
+            simpleHeaders r `shouldSatisfy` matchHeader "Content-Length" "22"
             simpleStatus r `shouldBe` ok200
 
         it "understands open-ended ranges" $
diff --git a/test/spec/Feature/Query/RpcSpec.hs b/test/spec/Feature/Query/RpcSpec.hs
index 7eef4513a..50375f9ed 100644
--- a/test/spec/Feature/Query/RpcSpec.hs
+++ b/test/spec/Feature/Query/RpcSpec.hs
@@ -31,18 +31,21 @@ spec =
           post "/rpc/getitemrange?limit=1&offset=1" [json| { "min": 2, "max": 4 } |]
              `shouldRespondWith` [json| [{"id":4}] |]
               { matchStatus = 200
-              , matchHeaders = ["Content-Range" <:> "1-1/*"]
+              , matchHeaders = [ "Content-Range" <:> "1-1/*"
+                               , "Content-Length" <:> "10" ]
               }
           get "/rpc/getitemrange?min=2&max=4&limit=1&offset=1"
              `shouldRespondWith` [json| [{"id":4}] |]
               { matchStatus = 200
-              , matchHeaders = ["Content-Range" <:> "1-1/*"]
+              , matchHeaders = [ "Content-Range" <:> "1-1/*"
+                               , "Content-Length" <:> "10"]
               }
           request methodHead "/rpc/getitemrange?min=2&max=4&limit=1&offset=1" mempty mempty
             `shouldRespondWith`
               ""
               { matchStatus = 200
               , matchHeaders = [ matchContentTypeJson
+                               , matchHeaderAbsent hContentLength
                                , "Content-Range" <:> "1-1/*" ]
               }
 
@@ -210,7 +213,8 @@ spec =
             "code":"PGRST202",
             "details":"Searched for the function test.sayhell without parameters, but no matches were found in the schema cache."} |]
           { matchStatus  = 404
-          , matchHeaders = [matchContentTypeJson]
+          , matchHeaders = [ "Content-Length" <:> "291"
+                           , matchContentTypeJson ]
           }
 
       it "should fail with 404 on unknown proc args" $ do
@@ -268,7 +272,8 @@ spec =
             "code":"PGRST203",
             "details":null} |]
           { matchStatus  = 300
-          , matchHeaders = [matchContentTypeJson]
+          , matchHeaders = [ "Content-Length" <:> "353"
+                           , matchContentTypeJson ]
           }
 
     it "works when having uppercase identifiers" $ do
@@ -465,7 +470,8 @@ spec =
           `shouldRespondWith`
             ""
             { matchStatus = 204
-            , matchHeaders = [matchHeaderAbsent hContentType]
+            , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength]
             }
 
       it "returns null for an integer with null value" $
@@ -613,7 +619,8 @@ spec =
           `shouldRespondWith`
           [json|{"message":"Cannot use the DELETE method on RPC","code":"PGRST101","details":null,"hint":null}|]
           { matchStatus  = 405
-          , matchHeaders = [matchContentTypeJson]
+          , matchHeaders = [ "Content-Length" <:> "94"
+                           , matchContentTypeJson ]
           }
       it "PATCH fails" $
         request methodPatch "/rpc/sayhello" [] ""
@@ -628,7 +635,8 @@ spec =
         `shouldRespondWith`
           ""
           { matchStatus = 204
-          , matchHeaders = [ matchHeaderAbsent hContentType ]
+          , matchHeaders = [ matchHeaderAbsent hContentType
+                           , matchHeaderAbsent hContentLength]
           }
 
       -- now the test
@@ -761,7 +769,8 @@ spec =
       get "/rpc/raise_pt402"
         `shouldRespondWith` [json|{ "hint": "Upgrade your plan", "details": "Quota exceeded", "code": "PT402", "message": "Payment Required" }|]
         { matchStatus  = 402
-        , matchHeaders = [matchContentTypeJson]
+        , matchHeaders = [ "Content-Length" <:> "99"
+                         , matchContentTypeJson ]
         }
 
     it "defaults to status 500 if RAISE code is PT not followed by a number" $
@@ -769,7 +778,8 @@ spec =
         `shouldRespondWith`
         [json|{"hint": null, "details": null, "code": "PT40A", "message": "Wrong"}|]
         { matchStatus  = 500
-        , matchHeaders = [ matchContentTypeJson ]
+        , matchHeaders = [ "Content-Length" <:> "61"
+                         , matchContentTypeJson ]
         }
 
     context "should work with an overloaded function" $ do
@@ -1024,7 +1034,8 @@ spec =
           `shouldRespondWith`
           [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value","code":"PGRST111","details":null,"hint":null}|]
           { matchStatus  = 500
-          , matchHeaders = [ matchContentTypeJson ]
+          , matchHeaders = [ "Content-Length" <:> "157"
+                           , matchContentTypeJson ]
           }
         get "/rpc/bad_guc_headers_2"
           `shouldRespondWith`
@@ -1051,6 +1062,7 @@ spec =
             ""
             { matchStatus = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Set-Cookie" <:> "sessionid=38afes7a8; HttpOnly; Path=/"
                              , "Set-Cookie" <:> "id=a3fWa; Expires=Wed, 21 Oct 2015 07:28:00 GMT; Secure; HttpOnly" ]
             }
@@ -1113,7 +1125,8 @@ spec =
             `shouldRespondWith`
             [json|{"message":"response.status guc must be a valid status code","code":"PGRST112","details":null,"hint":null}|]
             { matchStatus  = 500
-            , matchHeaders = [ matchContentTypeJson ]
+            , matchHeaders = [ "Content-Length" <:> "106"
+                             , matchContentTypeJson ]
             }
 
       context "single unnamed param" $ do
@@ -1291,7 +1304,8 @@ spec =
                 "details":"line 1: StartTag: invalid element name\n<\n ^"
               }|]
               { matchStatus  = 400
-              , matchHeaders = [matchContentTypeJson]
+              , matchHeaders = [ "Content-Length" <:> "118"
+                               , matchContentTypeJson ]
               }
 
     -- https://github.com/PostgREST/postgrest/issues/1586#issuecomment-696345442
@@ -1304,7 +1318,10 @@ spec =
         post "/rpc/char_param_insert" [json| { "char_": "abcdefg", "char_arr": "{abc,abcdefg}" } |]
            `shouldRespondWith`
              [json| {"code":"22001","details":null,"hint":null,"message":"value too long for type character(5)"} |]
-           { matchStatus = 400 }
+           { matchStatus = 400
+           , matchHeaders = [ "Content-Length" <:> "92"
+                            , matchContentTypeJson ]
+           }
 
       it "modifies the param type from bit to bit varying" $ do
         get "/rpc/bit_param_select?bit_=101010&bit_arr={101,101010}" `shouldRespondWith`
@@ -1314,7 +1331,10 @@ spec =
         post "/rpc/bit_param_insert" [json| { "bit_": "101010", "bit_arr": "{101,101010}" } |]
            `shouldRespondWith`
              [json| {"code":"22026","details":null,"hint":null,"message":"bit string length 6 does not match type bit(5)"} |]
-           { matchStatus = 400 }
+           { matchStatus = 400
+           , matchHeaders = [ "Content-Length" <:> "102"
+                            , matchContentTypeJson ]
+           }
 
     context "get message and details from raise sqlstate" $ do
       it "gets message and details from raise sqlstate PGRST" $ do
@@ -1369,7 +1389,10 @@ spec =
             "message":"Could not parse JSON in the \"RAISE SQLSTATE 'PGRST'\" error",
             "details":"Invalid JSON value for MESSAGE: 'INVALID'",
             "hint":"MESSAGE must be a JSON object with obligatory keys: 'code', 'message' and optional keys: 'details', 'hint'."}|]
-          { matchStatus = 500 }
+          { matchStatus = 500
+          , matchHeaders = [ "Content-Length" <:> "263"
+                           , matchContentTypeJson ]
+           }
 
       it "returns error for invalid JSON in the DETAIL option of the RAISE statement" $
         get "/rpc/raise_sqlstate_invalid_json_details" `shouldRespondWith`
@@ -1395,4 +1418,7 @@ spec =
       it "should return http status 500" $
         request methodGet "/rpc/temp_file_limit" [auth] "" `shouldRespondWith`
           [json|{"code":"53400","message":"temporary file size exceeds temp_file_limit (1kB)","details":null,"hint":null}|]
-          { matchStatus = 500 }
+          { matchStatus = 500
+          , matchHeaders = [ "Content-Length" <:> "105"
+                           , matchContentTypeJson ]
+          }
diff --git a/test/spec/Feature/Query/UpdateSpec.hs b/test/spec/Feature/Query/UpdateSpec.hs
index 43c8ff411..ee18e3208 100644
--- a/test/spec/Feature/Query/UpdateSpec.hs
+++ b/test/spec/Feature/Query/UpdateSpec.hs
@@ -20,7 +20,7 @@ spec = do
           `shouldRespondWith`
           [json| {"code":"PGRST205","details":null,"hint":"Perhaps you meant the table 'test.factories'","message":"Could not find the table 'test.fake' in the schema cache"} |]
           { matchStatus = 404
-          , matchHeaders = []
+          , matchHeaders = ["Content-Length" <:> "157"]
           }
 
 
@@ -31,7 +31,8 @@ spec = do
           `shouldRespondWith`
             ""
             { matchStatus  = 204,
-              matchHeaders = [matchHeaderAbsent hContentType]
+              matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength ]
             }
 
     context "with invalid json payload" $
@@ -40,7 +41,8 @@ spec = do
           `shouldRespondWith`
           [json|{"message":"Empty or invalid json","code":"PGRST102","details":null,"hint":null}|]
           { matchStatus  = 400,
-            matchHeaders = [matchContentTypeJson]
+            matchHeaders = [ matchContentTypeJson
+                           , "Content-Length" <:> "80"]
           }
 
     context "with no payload" $
@@ -59,6 +61,7 @@ spec = do
                      "\t \n \r { \"id\": 99 } \t \n \r "
           `shouldRespondWith` [json|[{"id":99}]|]
           { matchStatus  = 200
+          , matchHeaders = ["Content-Length" <:> "11"]
           }
 
     context "in a nonempty table" $ do
@@ -69,6 +72,7 @@ spec = do
             ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "0-0/*" ]
             }
 
@@ -78,7 +82,8 @@ spec = do
           `shouldRespondWith` "[]"
           {
             matchStatus  = 200,
-            matchHeaders = ["Preference-Applied" <:> "return=representation"]
+            matchHeaders = [ "Preference-Applied" <:> "return=representation"
+                           , "Content-Length" <:> "2"]
           }
 
       it "returns status code 200 when no rows updated" $
@@ -107,6 +112,7 @@ spec = do
             ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "0-1/*"
                              , "Preference-Applied" <:> "tx=commit" ]
             }
@@ -123,7 +129,8 @@ spec = do
           `shouldRespondWith`
             ""
             { matchStatus = 204
-            , matchHeaders = [matchHeaderAbsent hContentType]
+            , matchHeaders = [matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength ]
             }
 
       it "can set a column to NULL" $ do
@@ -207,6 +214,7 @@ spec = do
             ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "0-0/*"
                              , "Preference-Applied" <:> "return=minimal"]
             }
@@ -217,6 +225,7 @@ spec = do
             ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "0-0/*"
                              , "Preference-Applied" <:> "return=minimal"]
             }
@@ -230,6 +239,7 @@ spec = do
               ""
               { matchStatus  = 204
               , matchHeaders = [ matchHeaderAbsent hContentType
+                               , matchHeaderAbsent hContentLength
                                , "Content-Range" <:> "*/*" ]
               }
 
@@ -240,6 +250,7 @@ spec = do
               ""
               { matchStatus  = 204
               , matchHeaders = [ matchHeaderAbsent hContentType
+                               , matchHeaderAbsent hContentLength
                                , "Content-Range" <:> "*/*" ]
               }
 
@@ -250,6 +261,7 @@ spec = do
               ""
               { matchStatus  = 204
               , matchHeaders = [ matchHeaderAbsent hContentType
+                               , matchHeaderAbsent hContentLength
                                , "Content-Range" <:> "*/*" ]
               }
 
@@ -261,6 +273,7 @@ spec = do
               ""
               { matchStatus  = 204
               , matchHeaders = [ matchHeaderAbsent hContentType
+                               , matchHeaderAbsent hContentLength
                                , "Content-Range" <:> "*/*" ]
               }
 
@@ -271,6 +284,7 @@ spec = do
               ""
               { matchStatus  = 204
               , matchHeaders = [ matchHeaderAbsent hContentType
+                               , matchHeaderAbsent hContentLength
                                , "Content-Range" <:> "*/*" ]
               }
 
@@ -281,6 +295,7 @@ spec = do
               ""
               { matchStatus  = 204
               , matchHeaders = [ matchHeaderAbsent hContentType
+                               , matchHeaderAbsent hContentLength
                                , "Content-Range" <:> "*/*" ]
               }
 
@@ -350,7 +365,7 @@ spec = do
           `shouldRespondWith`
           [json| {"code":"PGRST205","details":null,"hint":"Perhaps you meant the table 'test.articles'","message":"Could not find the table 'test.garlic' in the schema cache"} |]
           { matchStatus  = 404
-          , matchHeaders = []
+          , matchHeaders = ["Content-Length" <:> "158"]
           }
 
       context "apply defaults on missing values" $ do
@@ -613,6 +628,7 @@ spec = do
           ""
           { matchStatus = 204
           , matchHeaders = [matchHeaderAbsent hContentType
+                           , matchHeaderAbsent hContentLength
                            , "Preference-Applied" <:> "return=minimal"]
           }
 
@@ -623,7 +639,8 @@ spec = do
         `shouldRespondWith`
           ""
           { matchStatus = 204
-          , matchHeaders = [matchHeaderAbsent hContentType]
+          , matchHeaders = [ matchHeaderAbsent hContentType
+                           , matchHeaderAbsent hContentLength ]
           }
 
   -- Data representations for payload parsing requires Postgres 10 or above.
@@ -636,6 +653,7 @@ spec = do
           ""
             { matchStatus  = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "Content-Range" <:> "0-0/*" ]
             }
 
diff --git a/test/spec/Feature/RollbackSpec.hs b/test/spec/Feature/RollbackSpec.hs
index d86176575..35f0b3f88 100644
--- a/test/spec/Feature/RollbackSpec.hs
+++ b/test/spec/Feature/RollbackSpec.hs
@@ -30,7 +30,9 @@ deleteItems =
     `shouldRespondWith`
       ""
       { matchStatus  = 204
-      , matchHeaders = [matchHeaderAbsent hContentType] }
+      , matchHeaders = [ matchHeaderAbsent hContentType
+                       , matchHeaderAbsent hContentLength ]
+      }
 
 preferDefault  = [("Prefer", "return=representation")]
 preferCommit   = [("Prefer", "return=representation"), ("Prefer", "tx=commit")]
@@ -262,4 +264,3 @@ forced = describe "tx-rollback-all = true, tx-allow-override = false" $ do
     preferRollback `shouldRespondToReads` withoutPreferenceApplied
     preferRollback `shouldNotPersistMutations` withoutPreferenceApplied
     preferRollback `shouldRaiseExceptions` withoutPreferenceApplied
-
diff --git a/test/spec/Feature/RpcPreRequestGucsSpec.hs b/test/spec/Feature/RpcPreRequestGucsSpec.hs
index 548ce18e5..d013d6015 100644
--- a/test/spec/Feature/RpcPreRequestGucsSpec.hs
+++ b/test/spec/Feature/RpcPreRequestGucsSpec.hs
@@ -56,6 +56,7 @@ spec =
             ""
             { matchStatus = 204
             , matchHeaders = [ matchHeaderAbsent hContentType
+                             , matchHeaderAbsent hContentLength
                              , "X-Custom-Header" <:> "mykey=myval" ]
             }
 
@@ -66,6 +67,7 @@ spec =
           ""
           { matchStatus = 204
           , matchHeaders = [ matchHeaderAbsent hContentType
+                           , matchHeaderAbsent hContentLength
                            , "X-Custom-Header" <:> "mykey=myval" ]
           }
 
@@ -75,6 +77,7 @@ spec =
           ""
           { matchStatus = 204
           , matchHeaders = [ matchHeaderAbsent hContentType
+                           , matchHeaderAbsent hContentLength
                            , "X-Custom-Header" <:> "mykey=myval" ]
           }
     it "can override the Content-Type header" $ do
diff --git a/test/spec/SpecHelper.hs b/test/spec/SpecHelper.hs
index d3bcc5fd3..6ecb7ff61 100644
--- a/test/spec/SpecHelper.hs
+++ b/test/spec/SpecHelper.hs
@@ -281,6 +281,9 @@ noBlankHeader = notElem mempty
 noProfileHeader :: [Header] -> Bool
 noProfileHeader headers = isNothing $ find ((== "Content-Profile") . fst) headers
 
+notZeroContentLength :: [Header] -> Bool
+notZeroContentLength headers = maybe False (/= "0") $ lookup hContentLength headers
+
 authHeader :: BS.ByteString -> BS.ByteString -> Header
 authHeader typ creds =
   (hAuthorization, typ <> " " <> creds)