diff --git a/postgrest.cabal b/postgrest.cabal
index 7394ff7fc..f5a22143d 100644
--- a/postgrest.cabal
+++ b/postgrest.cabal
@@ -158,13 +158,12 @@ test-suite spec
                       Feature.JsonOperatorSpec
                       Feature.NoJwtSpec
                       Feature.NonexistentSchemaSpec
-                      Feature.PgVersion95Spec
-                      Feature.PgVersion96Spec
                       Feature.ProxySpec
                       Feature.QueryLimitedSpec
                       Feature.QuerySpec
                       Feature.RangeSpec
                       Feature.RootSpec
+                      Feature.RpcPreRequestGucsSpec
                       Feature.RpcSpec
                       Feature.SingularSpec
                       Feature.StructureSpec
diff --git a/test/Feature/JsonOperatorSpec.hs b/test/Feature/JsonOperatorSpec.hs
index b9318d4bd..9f0d47f3e 100644
--- a/test/Feature/JsonOperatorSpec.hs
+++ b/test/Feature/JsonOperatorSpec.hs
@@ -7,7 +7,7 @@ import Test.Hspec
 import Test.Hspec.Wai
 import Test.Hspec.Wai.JSON
 
-import PostgREST.Types (PgVersion, pgVersion112, pgVersion121)
+import PostgREST.Types (PgVersion, pgVersion112, pgVersion121, pgVersion95)
 import Protolude       hiding (get)
 import SpecHelper
 
@@ -207,3 +207,47 @@ spec actualPgVersion = describe "json and jsonb operators" $ do
                    [json| { "data": { "escaped":" \"bar" } } |]
         `shouldRespondWith` [json| [{ "data": { "escaped":" \"bar" } }] |]
         { matchStatus  = 200 , matchHeaders = [] }
+
+  when (actualPgVersion >= pgVersion95) $
+    context "json array negative index" $ do
+      it "can select with negative indexes" $ do
+        get "/json_arr?select=data->>-1::int&id=in.(1,2)" `shouldRespondWith`
+          [json| [{"data":3}, {"data":6}] |]
+          { matchHeaders = [matchContentTypeJson] }
+        get "/json_arr?select=data->0->>-2::int&id=in.(3,4)" `shouldRespondWith`
+          [json| [{"data":8}, {"data":7}] |]
+          { matchHeaders = [matchContentTypeJson] }
+        get "/json_arr?select=data->-2->>a&id=in.(5,6)" `shouldRespondWith`
+          [json| [{"a":"A"}, {"a":"[1,2,3]"}] |]
+          { matchHeaders = [matchContentTypeJson] }
+
+      it "can filter with negative indexes" $ do
+        get "/json_arr?select=data&data->>-3=eq.1" `shouldRespondWith`
+          [json| [{"data":[1, 2, 3]}] |]
+          { matchHeaders = [matchContentTypeJson] }
+        get "/json_arr?select=data&data->-1->>-3=eq.11" `shouldRespondWith`
+          [json| [{"data":[[9, 8, 7], [11, 12, 13]]}] |]
+          { matchHeaders = [matchContentTypeJson] }
+        get "/json_arr?select=data&data->-1->>b=eq.B" `shouldRespondWith`
+          [json| [{"data":[{"a": "A"}, {"b": "B"}]}] |]
+          { matchHeaders = [matchContentTypeJson] }
+        get "/json_arr?select=data&data->-1->b->>-1=eq.5" `shouldRespondWith`
+          [json| [{"data":[{"a": [1,2,3]}, {"b": [4,5]}]}] |]
+          { matchHeaders = [matchContentTypeJson] }
+
+      it "should fail on badly formed negatives" $ do
+        get "/json_arr?select=data->>-78xy" `shouldRespondWith`
+          [json|
+            {"details": "unexpected 'x' expecting digit, \"->\", \"::\" or end of input",
+             "message": "\"failed to parse select parameter (data->>-78xy)\" (line 1, column 11)"} |]
+          { matchStatus = 400, matchHeaders = [matchContentTypeJson] }
+        get "/json_arr?select=data->>--34" `shouldRespondWith`
+          [json|
+            {"details": "unexpected \"-\" expecting digit",
+             "message": "\"failed to parse select parameter (data->>--34)\" (line 1, column 9)"} |]
+          { matchStatus = 400, matchHeaders = [matchContentTypeJson] }
+        get "/json_arr?select=data->>-xy-4" `shouldRespondWith`
+          [json|
+            {"details":"unexpected \"x\" expecting digit",
+             "message":"\"failed to parse select parameter (data->>-xy-4)\" (line 1, column 9)"} |]
+          { matchStatus = 400, matchHeaders = [matchContentTypeJson] }
diff --git a/test/Feature/PgVersion95Spec.hs b/test/Feature/PgVersion95Spec.hs
deleted file mode 100644
index 31f889234..000000000
--- a/test/Feature/PgVersion95Spec.hs
+++ /dev/null
@@ -1,55 +0,0 @@
-module Feature.PgVersion95Spec where
-
-import Network.Wai (Application)
-
-import Test.Hspec
-import Test.Hspec.Wai
-import Test.Hspec.Wai.JSON
-
-import Protolude  hiding (get)
-import SpecHelper
-
-spec :: SpecWith ((), Application)
-spec = describe "features supported on PostgreSQL 9.5" $
-  context "json array negative index" $ do
-    it "can select with negative indexes" $ do
-      get "/json_arr?select=data->>-1::int&id=in.(1,2)" `shouldRespondWith`
-        [json| [{"data":3}, {"data":6}] |]
-        { matchHeaders = [matchContentTypeJson] }
-      get "/json_arr?select=data->0->>-2::int&id=in.(3,4)" `shouldRespondWith`
-        [json| [{"data":8}, {"data":7}] |]
-        { matchHeaders = [matchContentTypeJson] }
-      get "/json_arr?select=data->-2->>a&id=in.(5,6)" `shouldRespondWith`
-        [json| [{"a":"A"}, {"a":"[1,2,3]"}] |]
-        { matchHeaders = [matchContentTypeJson] }
-
-    it "can filter with negative indexes" $ do
-      get "/json_arr?select=data&data->>-3=eq.1" `shouldRespondWith`
-        [json| [{"data":[1, 2, 3]}] |]
-        { matchHeaders = [matchContentTypeJson] }
-      get "/json_arr?select=data&data->-1->>-3=eq.11" `shouldRespondWith`
-        [json| [{"data":[[9, 8, 7], [11, 12, 13]]}] |]
-        { matchHeaders = [matchContentTypeJson] }
-      get "/json_arr?select=data&data->-1->>b=eq.B" `shouldRespondWith`
-        [json| [{"data":[{"a": "A"}, {"b": "B"}]}] |]
-        { matchHeaders = [matchContentTypeJson] }
-      get "/json_arr?select=data&data->-1->b->>-1=eq.5" `shouldRespondWith`
-        [json| [{"data":[{"a": [1,2,3]}, {"b": [4,5]}]}] |]
-        { matchHeaders = [matchContentTypeJson] }
-
-    it "should fail on badly formed negatives" $ do
-      get "/json_arr?select=data->>-78xy" `shouldRespondWith`
-        [json|
-          {"details": "unexpected 'x' expecting digit, \"->\", \"::\" or end of input",
-           "message": "\"failed to parse select parameter (data->>-78xy)\" (line 1, column 11)"} |]
-        { matchStatus = 400, matchHeaders = [matchContentTypeJson] }
-      get "/json_arr?select=data->>--34" `shouldRespondWith`
-        [json|
-          {"details": "unexpected \"-\" expecting digit",
-           "message": "\"failed to parse select parameter (data->>--34)\" (line 1, column 9)"} |]
-        { matchStatus = 400, matchHeaders = [matchContentTypeJson] }
-      get "/json_arr?select=data->>-xy-4" `shouldRespondWith`
-        [json|
-          {"details":"unexpected \"x\" expecting digit",
-           "message":"\"failed to parse select parameter (data->>-xy-4)\" (line 1, column 9)"} |]
-        { matchStatus = 400, matchHeaders = [matchContentTypeJson] }
diff --git a/test/Feature/PgVersion96Spec.hs b/test/Feature/PgVersion96Spec.hs
deleted file mode 100644
index cafac34fe..000000000
--- a/test/Feature/PgVersion96Spec.hs
+++ /dev/null
@@ -1,216 +0,0 @@
-module Feature.PgVersion96Spec where
-
-import Network.HTTP.Types
-import Network.Wai        (Application)
-import Network.Wai.Test   (SResponse (simpleHeaders))
-
-import Test.Hspec
-import Test.Hspec.Wai
-import Test.Hspec.Wai.JSON
-
-import Protolude  hiding (get)
-import SpecHelper
-
-spec :: SpecWith ((), Application)
-spec =
-  describe "features supported on PostgreSQL 9.6" $ do
-    context "GUC headers on function calls" $ do
-      it "succeeds setting the headers" $ do
-        get "/rpc/get_projects_and_guc_headers?id=eq.2&select=id"
-          `shouldRespondWith` [json|[{"id": 2}]|]
-          {matchHeaders = [
-              matchContentTypeJson,
-              "X-Test"   <:> "key1=val1; someValue; key2=val2",
-              "X-Test-2" <:> "key1=val1"]}
-        get "/rpc/get_int_and_guc_headers?num=1"
-          `shouldRespondWith` [json|1|]
-          {matchHeaders = [
-              matchContentTypeJson,
-              "X-Test"   <:> "key1=val1; someValue; key2=val2",
-              "X-Test-2" <:> "key1=val1"]}
-        post "/rpc/get_int_and_guc_headers" [json|{"num": 1}|]
-          `shouldRespondWith` [json|1|]
-          {matchHeaders = [
-              matchContentTypeJson,
-              "X-Test"   <:> "key1=val1; someValue; key2=val2",
-              "X-Test-2" <:> "key1=val1"]}
-
-      it "fails when setting headers with wrong json structure" $ do
-        get "/rpc/bad_guc_headers_1"
-          `shouldRespondWith`
-          [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
-          { matchStatus  = 500
-          , matchHeaders = [ matchContentTypeJson ]
-          }
-        get "/rpc/bad_guc_headers_2"
-          `shouldRespondWith`
-          [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
-          { matchStatus  = 500
-          , matchHeaders = [ matchContentTypeJson ]
-          }
-        get "/rpc/bad_guc_headers_3"
-          `shouldRespondWith`
-          [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
-          { matchStatus  = 500
-          , matchHeaders = [ matchContentTypeJson ]
-          }
-        post "/rpc/bad_guc_headers_1" [json|{}|]
-          `shouldRespondWith`
-          [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
-          { matchStatus  = 500
-          , matchHeaders = [ matchContentTypeJson ]
-          }
-
-      it "can set the same http header twice" $
-        get "/rpc/set_cookie_twice"
-          `shouldRespondWith` "null"
-          {matchHeaders = [
-              matchContentTypeJson,
-              "Set-Cookie" <:> "sessionid=38afes7a8; HttpOnly; Path=/",
-              "Set-Cookie" <:> "id=a3fWa; Expires=Wed, 21 Oct 2015 07:28:00 GMT; Secure; HttpOnly"]}
-
-    context "GUC headers on all other methods via pre-request" $ do
-      it "succeeds setting the headers on GET and HEAD" $ do
-        request methodGet "/items?id=eq.1" [("User-Agent", "MSIE 6.0")] mempty
-          `shouldRespondWith` [json|[{"id": 1}]|]
-          {matchHeaders = [
-              matchContentTypeJson,
-              "Cache-Control" <:> "no-cache, no-store, must-revalidate"]}
-
-        request methodHead "/items?id=eq.1" [("User-Agent", "MSIE 7.0")] mempty
-          `shouldRespondWith` ""
-          {matchHeaders = ["Cache-Control" <:> "no-cache, no-store, must-revalidate"]}
-
-        request methodHead "/projects" [("Accept", "text/csv")] mempty
-          `shouldRespondWith` ""
-          {matchHeaders = ["Content-Disposition" <:> "attachment; filename=projects.csv"]}
-
-      it "succeeds setting the headers on POST" $
-        request methodPost "/items" [] [json|[{"id": 11111}]|]
-          `shouldRespondWith` ""
-          { matchStatus = 201
-          , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
-          }
-
-      it "succeeds setting the headers on PATCH" $
-        request methodPatch "/items?id=eq.11111" [] [json|[{"id": 11111}]|]
-          `shouldRespondWith` ""
-          { matchStatus = 204
-          , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
-          }
-
-      it "succeeds setting the headers on PUT" $
-        request methodPut "/items?id=eq.11111" [] [json|[{"id": 11111}]|]
-          `shouldRespondWith` ""
-          { matchStatus = 204
-          , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
-          }
-
-      it "succeeds setting the headers on DELETE" $
-        request methodDelete "/items?id=eq.11111" [] mempty
-          `shouldRespondWith` ""
-          { matchStatus = 204
-          , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
-          }
-
-    context "Override provided headers by using GUC headers" $ do
-      it "can override the Content-Type header" $ do
-        request methodHead "/clients?id=eq.1" [] mempty
-          `shouldRespondWith` ""
-          { matchStatus = 200
-          , matchHeaders = ["Content-Type" <:> "application/geo+json"]
-          }
-        request methodHead "/rpc/getallprojects" [] mempty
-          `shouldRespondWith` ""
-          { matchStatus = 200
-          , matchHeaders = ["Content-Type" <:> "application/geo+json"]
-          }
-
-      it "can override the Location header" $
-        request methodPost "/stuff" [] [json|[{"id": 1, "name": "stuff 1"}]|]
-          `shouldRespondWith` ""
-          { matchStatus = 201
-          , matchHeaders = ["Location" <:> "/stuff?id=eq.1&overriden=true"]
-          }
-
-    -- On https://github.com/PostgREST/postgrest/issues/1427#issuecomment-595907535
-    -- it was reported that blank headers ` : ` where added and that cause proxies to fail the requests.
-    -- These tests are to ensure no blank headers are added.
-    context "Blank headers bug" $ do
-      it "shouldn't add blank headers on POST" $ do
-        r <- request methodPost "/loc_test" [] [json|{"id": "1", "c": "c1"}|]
-        liftIO $ do
-          let respHeaders = simpleHeaders r
-          respHeaders `shouldSatisfy` noBlankHeader
-
-      it "shouldn't add blank headers on PATCH" $ do
-        r <- request methodPatch "/loc_test?id=eq.1" [] [json|{"c": "c2"}|]
-        liftIO $ do
-          let respHeaders = simpleHeaders r
-          respHeaders `shouldSatisfy` noBlankHeader
-
-      it "shouldn't add blank headers on GET" $ do
-        r <- request methodGet "/loc_test" [] ""
-        liftIO $ do
-          let respHeaders = simpleHeaders r
-          respHeaders `shouldSatisfy` noBlankHeader
-
-      it "shouldn't add blank headers on DELETE" $ do
-        r <- request methodDelete "/loc_test?id=eq.1" [] ""
-        liftIO $ do
-          let respHeaders = simpleHeaders r
-          respHeaders `shouldSatisfy` noBlankHeader
-
-    context "GUC status override" $ do
-      it "can override the status on RPC" $
-        get "/rpc/send_body_status_403"
-          `shouldRespondWith`
-          [json|{"message" : "invalid user or password"}|]
-          { matchStatus  = 403
-          , matchHeaders = [ matchContentTypeJson ]
-          }
-
-      it "can override the status through trigger" $
-        request methodPatch "/stuff?id=eq.1" [] [json|[{"name": "updated stuff 1"}]|]
-          `shouldRespondWith` 205
-
-      it "fails when setting invalid status guc" $
-        get "/rpc/send_bad_status"
-          `shouldRespondWith`
-          [json|{"message":"response.status guc must be a valid status code"}|]
-          { matchStatus  = 500
-          , matchHeaders = [ matchContentTypeJson ]
-          }
-
-    context "Use of the phraseto_tsquery function" $ do
-      it "finds matches" $
-        get "/tsearch?text_search_vector=phfts.The%20Fat%20Cats" `shouldRespondWith`
-          [json| [{"text_search_vector": "'ate':3 'cat':2 'fat':1 'rat':4" }] |]
-          { matchHeaders = [matchContentTypeJson] }
-
-      it "finds matches with different dictionaries" $
-        get "/tsearch?text_search_vector=phfts(german).Art%20Spass" `shouldRespondWith`
-          [json| [{"text_search_vector": "'art':4 'spass':5 'unmog':7" }] |]
-          { matchHeaders = [matchContentTypeJson] }
-
-      it "can be negated with not operator" $
-        get "/tsearch?text_search_vector=not.phfts(english).The%20Fat%20Cats" `shouldRespondWith`
-          [json| [
-            {"text_search_vector": "'fun':5 'imposs':9 'kind':3"},
-            {"text_search_vector": "'also':2 'fun':3 'possibl':8"},
-            {"text_search_vector": "'amus':5 'fair':7 'impossibl':9 'peu':4"},
-            {"text_search_vector": "'art':4 'spass':5 'unmog':7"}]|]
-          { matchHeaders = [matchContentTypeJson] }
-
-      it "can be used with or query param" $
-        get "/tsearch?or=(text_search_vector.phfts(german).Art%20Spass, text_search_vector.phfts(french).amusant, text_search_vector.fts(english).impossible)" `shouldRespondWith`
-          [json|[
-            {"text_search_vector": "'fun':5 'imposs':9 'kind':3" },
-            {"text_search_vector": "'amus':5 'fair':7 'impossibl':9 'peu':4" },
-            {"text_search_vector": "'art':4 'spass':5 'unmog':7"}
-          ]|] { matchHeaders = [matchContentTypeJson] }
-
-      it "should work when used with GET RPC" $
-        get "/rpc/get_tsearch?text_search_vector=phfts(english).impossible" `shouldRespondWith`
-          [json|[{"text_search_vector":"'fun':5 'imposs':9 'kind':3"}]|]
-          { matchHeaders = [matchContentTypeJson] }
diff --git a/test/Feature/QuerySpec.hs b/test/Feature/QuerySpec.hs
index 4e3d1260c..12f0d7a24 100644
--- a/test/Feature/QuerySpec.hs
+++ b/test/Feature/QuerySpec.hs
@@ -10,7 +10,7 @@ import Test.Hspec.Wai.JSON
 
 import Text.Heredoc
 
-import PostgREST.Types (PgVersion, pgVersion112, pgVersion121)
+import PostgREST.Types (PgVersion, pgVersion96, pgVersion112, pgVersion121)
 import Protolude       hiding (get)
 import SpecHelper
 
@@ -183,6 +183,35 @@ spec actualPgVersion = do
                     {"text_search_vector": "'art':4 'spass':5 'unmog':7"}]|]
                   { matchHeaders = [matchContentTypeJson] }
 
+      when (actualPgVersion >= pgVersion96) $
+        context "Use of the phraseto_tsquery function" $ do
+          it "finds matches" $
+            get "/tsearch?text_search_vector=phfts.The%20Fat%20Cats" `shouldRespondWith`
+              [json| [{"text_search_vector": "'ate':3 'cat':2 'fat':1 'rat':4" }] |]
+              { matchHeaders = [matchContentTypeJson] }
+
+          it "finds matches with different dictionaries" $
+            get "/tsearch?text_search_vector=phfts(german).Art%20Spass" `shouldRespondWith`
+              [json| [{"text_search_vector": "'art':4 'spass':5 'unmog':7" }] |]
+              { matchHeaders = [matchContentTypeJson] }
+
+          it "can be negated with not operator" $
+            get "/tsearch?text_search_vector=not.phfts(english).The%20Fat%20Cats" `shouldRespondWith`
+              [json| [
+                {"text_search_vector": "'fun':5 'imposs':9 'kind':3"},
+                {"text_search_vector": "'also':2 'fun':3 'possibl':8"},
+                {"text_search_vector": "'amus':5 'fair':7 'impossibl':9 'peu':4"},
+                {"text_search_vector": "'art':4 'spass':5 'unmog':7"}]|]
+              { matchHeaders = [matchContentTypeJson] }
+
+          it "can be used with or query param" $
+            get "/tsearch?or=(text_search_vector.phfts(german).Art%20Spass, text_search_vector.phfts(french).amusant, text_search_vector.fts(english).impossible)" `shouldRespondWith`
+              [json|[
+                {"text_search_vector": "'fun':5 'imposs':9 'kind':3" },
+                {"text_search_vector": "'amus':5 'fair':7 'impossibl':9 'peu':4" },
+                {"text_search_vector": "'art':4 'spass':5 'unmog':7"}
+              ]|] { matchHeaders = [matchContentTypeJson] }
+
     it "matches with computed column" $
       get "/items?always_true=eq.true&order=id.asc" `shouldRespondWith`
         [json| [{"id":1},{"id":2},{"id":3},{"id":4},{"id":5},{"id":6},{"id":7},{"id":8},{"id":9},{"id":10},{"id":11},{"id":12},{"id":13},{"id":14},{"id":15}] |]
diff --git a/test/Feature/RpcPreRequestGucsSpec.hs b/test/Feature/RpcPreRequestGucsSpec.hs
new file mode 100644
index 000000000..77ff5120b
--- /dev/null
+++ b/test/Feature/RpcPreRequestGucsSpec.hs
@@ -0,0 +1,72 @@
+module Feature.RpcPreRequestGucsSpec where
+
+import qualified Data.ByteString.Lazy as BL (empty)
+
+import Network.Wai      (Application)
+import Network.Wai.Test (SResponse (simpleBody, simpleHeaders, simpleStatus))
+
+import Network.HTTP.Types
+import Test.Hspec          hiding (pendingWith)
+import Test.Hspec.Wai
+import Test.Hspec.Wai.JSON
+import Text.Heredoc
+
+import Protolude       hiding (get)
+import SpecHelper
+
+spec :: SpecWith ((), Application)
+spec =
+  describe "GUC headers on all methods via pre-request" $ do
+    it "succeeds setting the headers on POST" $
+      request methodPost "/items" [] [json|[{"id": 11111}]|]
+        `shouldRespondWith` ""
+        { matchStatus = 201
+        , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
+        }
+
+    it "succeeds setting the headers on GET and HEAD" $ do
+      request methodGet "/items?id=eq.11111" [("User-Agent", "MSIE 6.0")] mempty
+        `shouldRespondWith` [json|[{"id": 11111}]|]
+        {matchHeaders = [
+            matchContentTypeJson,
+            "Cache-Control" <:> "no-cache, no-store, must-revalidate"]}
+
+      request methodHead "/items?id=eq.11111" [("User-Agent", "MSIE 7.0")] mempty
+        `shouldRespondWith` ""
+        {matchHeaders = ["Cache-Control" <:> "no-cache, no-store, must-revalidate"]}
+
+      request methodHead "/projects" [("Accept", "text/csv")] mempty
+        `shouldRespondWith` ""
+        {matchHeaders = ["Content-Disposition" <:> "attachment; filename=projects.csv"]}
+
+    it "succeeds setting the headers on PATCH" $
+      request methodPatch "/items?id=eq.11111" [] [json|[{"id": 11111}]|]
+        `shouldRespondWith` ""
+        { matchStatus = 204
+        , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
+        }
+
+    it "succeeds setting the headers on PUT" $
+      request methodPut "/items?id=eq.11111" [] [json|[{"id": 11111}]|]
+        `shouldRespondWith` ""
+        { matchStatus = 204
+        , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
+        }
+
+    it "succeeds setting the headers on DELETE" $
+      request methodDelete "/items?id=eq.11111" [] mempty
+        `shouldRespondWith` ""
+        { matchStatus = 204
+        , matchHeaders = ["X-Custom-Header" <:> "mykey=myval"]
+        }
+    it "can override the Content-Type header" $ do
+      request methodHead "/clients?id=eq.1" [] mempty
+        `shouldRespondWith` ""
+        { matchStatus = 200
+        , matchHeaders = ["Content-Type" <:> "application/custom+json"]
+        }
+      request methodHead "/rpc/getallprojects" [] mempty
+        `shouldRespondWith` ""
+        { matchStatus = 200
+        , matchHeaders = ["Content-Type" <:> "application/custom+json"]
+        }
diff --git a/test/Feature/RpcSpec.hs b/test/Feature/RpcSpec.hs
index 2251d7813..d04134de3 100644
--- a/test/Feature/RpcSpec.hs
+++ b/test/Feature/RpcSpec.hs
@@ -3,7 +3,7 @@ module Feature.RpcSpec where
 import qualified Data.ByteString.Lazy as BL (empty)
 
 import Network.Wai      (Application)
-import Network.Wai.Test (SResponse (simpleBody, simpleStatus))
+import Network.Wai.Test (SResponse (simpleBody, simpleStatus, simpleHeaders))
 
 import Network.HTTP.Types
 import Test.Hspec          hiding (pendingWith)
@@ -12,7 +12,8 @@ import Test.Hspec.Wai.JSON
 import Text.Heredoc
 
 import PostgREST.Types (PgVersion, pgVersion100, pgVersion109,
-                        pgVersion110, pgVersion112, pgVersion114)
+                        pgVersion110, pgVersion112, pgVersion114,
+                        pgVersion96)
 import Protolude       hiding (get)
 import SpecHelper
 
@@ -787,7 +788,125 @@ spec actualPgVersion =
                 [json|[{"text_search_vector":"'fun':5 'imposs':9 'kind':3"}]|]
                 { matchHeaders = [matchContentTypeJson] }
 
+      when (actualPgVersion >= pgVersion96) $
+        it "should work with the phraseto_tsquery function" $
+          get "/rpc/get_tsearch?text_search_vector=phfts(english).impossible" `shouldRespondWith`
+            [json|[{"text_search_vector":"'fun':5 'imposs':9 'kind':3"}]|]
+            { matchHeaders = [matchContentTypeJson] }
+
     it "should work with an argument of custom type in public schema" $
         get "/rpc/test_arg?my_arg=something" `shouldRespondWith`
           [json|"foobar"|]
           { matchHeaders = [matchContentTypeJson] }
+
+    when (actualPgVersion >= pgVersion96) $ do
+      context "GUC headers on function calls" $ do
+        it "succeeds setting the headers" $ do
+          get "/rpc/get_projects_and_guc_headers?id=eq.2&select=id"
+            `shouldRespondWith` [json|[{"id": 2}]|]
+            {matchHeaders = [
+                matchContentTypeJson,
+                "X-Test"   <:> "key1=val1; someValue; key2=val2",
+                "X-Test-2" <:> "key1=val1"]}
+          get "/rpc/get_int_and_guc_headers?num=1"
+            `shouldRespondWith` [json|1|]
+            {matchHeaders = [
+                matchContentTypeJson,
+                "X-Test"   <:> "key1=val1; someValue; key2=val2",
+                "X-Test-2" <:> "key1=val1"]}
+          post "/rpc/get_int_and_guc_headers" [json|{"num": 1}|]
+            `shouldRespondWith` [json|1|]
+            {matchHeaders = [
+                matchContentTypeJson,
+                "X-Test"   <:> "key1=val1; someValue; key2=val2",
+                "X-Test-2" <:> "key1=val1"]}
+
+        it "fails when setting headers with wrong json structure" $ do
+          get "/rpc/bad_guc_headers_1"
+            `shouldRespondWith`
+            [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
+            { matchStatus  = 500
+            , matchHeaders = [ matchContentTypeJson ]
+            }
+          get "/rpc/bad_guc_headers_2"
+            `shouldRespondWith`
+            [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
+            { matchStatus  = 500
+            , matchHeaders = [ matchContentTypeJson ]
+            }
+          get "/rpc/bad_guc_headers_3"
+            `shouldRespondWith`
+            [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
+            { matchStatus  = 500
+            , matchHeaders = [ matchContentTypeJson ]
+            }
+          post "/rpc/bad_guc_headers_1" [json|{}|]
+            `shouldRespondWith`
+            [json|{"message":"response.headers guc must be a JSON array composed of objects with a single key and a string value"}|]
+            { matchStatus  = 500
+            , matchHeaders = [ matchContentTypeJson ]
+            }
+
+        it "can set the same http header twice" $
+          get "/rpc/set_cookie_twice"
+            `shouldRespondWith` "null"
+            {matchHeaders = [
+                matchContentTypeJson,
+                "Set-Cookie" <:> "sessionid=38afes7a8; HttpOnly; Path=/",
+                "Set-Cookie" <:> "id=a3fWa; Expires=Wed, 21 Oct 2015 07:28:00 GMT; Secure; HttpOnly"]}
+
+      it "can override the Location header on a trigger" $
+        request methodPost "/stuff" [] [json|[{"id": 1, "name": "stuff 1"}]|]
+          `shouldRespondWith` ""
+          { matchStatus = 201
+          , matchHeaders = ["Location" <:> "/stuff?id=eq.1&overriden=true"]
+          }
+
+      -- On https://github.com/PostgREST/postgrest/issues/1427#issuecomment-595907535
+      -- it was reported that blank headers ` : ` where added and that cause proxies to fail the requests.
+      -- These tests are to ensure no blank headers are added.
+      context "Blank headers bug" $ do
+        it "shouldn't add blank headers on POST" $ do
+          r <- request methodPost "/loc_test" [] [json|{"id": "1", "c": "c1"}|]
+          liftIO $ do
+            let respHeaders = simpleHeaders r
+            respHeaders `shouldSatisfy` noBlankHeader
+
+        it "shouldn't add blank headers on PATCH" $ do
+          r <- request methodPatch "/loc_test?id=eq.1" [] [json|{"c": "c2"}|]
+          liftIO $ do
+            let respHeaders = simpleHeaders r
+            respHeaders `shouldSatisfy` noBlankHeader
+
+        it "shouldn't add blank headers on GET" $ do
+          r <- request methodGet "/loc_test" [] ""
+          liftIO $ do
+            let respHeaders = simpleHeaders r
+            respHeaders `shouldSatisfy` noBlankHeader
+
+        it "shouldn't add blank headers on DELETE" $ do
+          r <- request methodDelete "/loc_test?id=eq.1" [] ""
+          liftIO $ do
+            let respHeaders = simpleHeaders r
+            respHeaders `shouldSatisfy` noBlankHeader
+
+      context "GUC status override" $ do
+        it "can override the status on RPC" $
+          get "/rpc/send_body_status_403"
+            `shouldRespondWith`
+            [json|{"message" : "invalid user or password"}|]
+            { matchStatus  = 403
+            , matchHeaders = [ matchContentTypeJson ]
+            }
+
+        it "can override the status through trigger" $
+          request methodPatch "/stuff?id=eq.1" [] [json|[{"name": "updated stuff 1"}]|]
+            `shouldRespondWith` 205
+
+        it "fails when setting invalid status guc" $
+          get "/rpc/send_bad_status"
+            `shouldRespondWith`
+            [json|{"message":"response.status guc must be a valid status code"}|]
+            { matchStatus  = 500
+            , matchHeaders = [ matchContentTypeJson ]
+            }
diff --git a/test/Main.hs b/test/Main.hs
index 200fd27fc..2d0150745 100644
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -36,14 +36,13 @@ import qualified Feature.JsonOperatorSpec
 import qualified Feature.MultipleSchemaSpec
 import qualified Feature.NoJwtSpec
 import qualified Feature.NonexistentSchemaSpec
-import qualified Feature.PgVersion95Spec
-import qualified Feature.PgVersion96Spec
 import qualified Feature.ProxySpec
 import qualified Feature.QueryLimitedSpec
 import qualified Feature.QuerySpec
 import qualified Feature.RangeSpec
 import qualified Feature.RawOutputTypesSpec
 import qualified Feature.RootSpec
+import qualified Feature.RpcPreRequestGucsSpec
 import qualified Feature.RpcSpec
 import qualified Feature.SingularSpec
 import qualified Feature.StructureSpec
@@ -110,7 +109,6 @@ main = do
         , ("Feature.StructureSpec"           , Feature.StructureSpec.spec)
         , ("Feature.AndOrParamsSpec"         , Feature.AndOrParamsSpec.spec actualPgVersion)
         , ("Feature.UpsertSpec"              , Feature.UpsertSpec.spec)
-        , ("Feature.PgVersion95Spec"         , Feature.PgVersion95Spec.spec)
         ]
 
       mutSpecs = uncurry describe <$> [
@@ -173,12 +171,13 @@ main = do
     before extraSearchPathApp $
       describe "Feature.ExtraSearchPathSpec" Feature.ExtraSearchPathSpec.spec
 
-    -- this test runs with a root spec function override
+
     when (actualPgVersion >= pgVersion96) $ do
+      -- this test runs with a root spec function override
       before rootSpecApp $
         describe "Feature.RootSpec" Feature.RootSpec.spec
       before responseHeadersApp $
-        describe "Feature.PgVersion96Spec" Feature.PgVersion96Spec.spec
+        describe "Feature.RpcPreRequestGucsSpec" Feature.RpcPreRequestGucsSpec.spec
 
     -- this test runs with multiple schemas
     before multipleSchemaApp $
diff --git a/test/fixtures/schema.sql b/test/fixtures/schema.sql
index ea1cd48fb..9d848c930 100755
--- a/test/fixtures/schema.sql
+++ b/test/fixtures/schema.sql
@@ -1699,19 +1699,21 @@ declare
   user_agent text := current_setting('request.header.user-agent', true);
   req_path   text := current_setting('request.path', true);
   req_accept text := current_setting('request.header.accept', true);
+  req_method text := current_setting('request.method', true);
 begin
   if user_agent similar to 'MSIE (6.0|7.0)' then
     perform set_config('response.headers',
-      '[{"Cache-Control": "no-cache, no-store, must-revalidate"}]', false);
+      '[{"Cache-Control": "no-cache, no-store, must-revalidate"}]', true);
   elsif req_path similar to '/(items|projects)' and req_accept = 'text/csv' then
     perform set_config('response.headers',
-      format('[{"Content-Disposition": "attachment; filename=%s.csv"}]', trim('/' from req_path)), false);
+      format('[{"Content-Disposition": "attachment; filename=%s.csv"}]', trim('/' from req_path)), true);
   elsif req_path similar to '/(clients|rpc/getallprojects)' then
     perform set_config('response.headers',
-      '[{"Content-Type": "application/geo+json"}]', false);
-  else
+      '[{"Content-Type": "application/custom+json"}]', true);
+  elsif req_path = '/items' and
+        req_method similar to 'POST|PATCH|PUT|DELETE' then
     perform set_config('response.headers',
-      '[{"X-Custom-Header": "mykey=myval"}]', false);
+      '[{"X-Custom-Header": "mykey=myval"}]', true);
   end if;
 end; $$ language plpgsql;