diff --git a/main/Main.hs b/main/Main.hs
index 54410264e..d89ad3b36 100644
--- a/main/Main.hs
+++ b/main/Main.hs
@@ -33,7 +33,8 @@ import PostgREST.OpenAPI     (isMalformedProxyUri)
 import PostgREST.Types       (ConnectionStatus (..), DbStructure,
                               PgVersion (..), Schema,
                               minimumPgVersion)
-import Protolude             hiding (hPutStrLn, head, replace)
+import Protolude             hiding (hPutStrLn, head, replace, toS)
+import Protolude.Conv        (toS)
 
 
 #ifndef mingw32_HOST_OS
diff --git a/postgrest.cabal b/postgrest.cabal
index 6e5dc62aa..49b66922f 100644
--- a/postgrest.cabal
+++ b/postgrest.cabal
@@ -72,7 +72,7 @@ library
                     , network-uri               >= 2.6.1 && < 2.8
                     , optparse-applicative      >= 0.13 && < 0.16
                     , parsec                    >= 3.1.11 && < 3.2
-                    , protolude                 >= 0.2.4 && < 0.3
+                    , protolude                 >= 0.3 && < 0.4
                     , regex-tdfa                >= 1.2.2 && < 1.4
                     , scientific                >= 0.3.4 && < 0.4
                     , swagger2                  >= 2.4 && < 2.6
@@ -110,7 +110,7 @@ executable postgrest
                     , hasql-transaction >= 0.7.2 && < 1.1
                     , network           < 3.2
                     , postgrest
-                    , protolude         >= 0.2.4 && < 0.3
+                    , protolude         >= 0.3 && < 0.4
                     , retry             >= 0.7.4 && < 0.9
                     , text              >= 1.2.2 && < 1.3
                     , time              >= 1.6 && < 1.11
@@ -187,7 +187,7 @@ test-suite spec
                     , monad-control     >= 1.0.1 && < 1.1
                     , postgrest
                     , process           >= 1.4.2 && < 1.7
-                    , protolude         >= 0.2.4 && < 0.3
+                    , protolude         >= 0.3 && < 0.4
                     , regex-tdfa        >= 1.2.2 && < 1.4
                     , text              >= 1.2.2 && < 1.3
                     , time              >= 1.6 && < 1.11
@@ -231,7 +231,7 @@ Test-Suite spec-querycost
                      , monad-control     >= 1.0.1 && < 1.1
                      , postgrest
                      , process           >= 1.4.2 && < 1.7
-                     , protolude         >= 0.2.4 && < 0.3
+                     , protolude         >= 0.3 && < 0.4
                      , regex-tdfa        >= 1.2.2 && < 1.4
                      , text              >= 1.2.2 && < 1.3
                      , time              >= 1.6 && < 1.11
diff --git a/src/PostgREST/ApiRequest.hs b/src/PostgREST/ApiRequest.hs
index 324ba42a5..8b8a10658 100644
--- a/src/PostgREST/ApiRequest.hs
+++ b/src/PostgREST/ApiRequest.hs
@@ -49,7 +49,8 @@ import PostgREST.RangeQuery (NonnegRange, allRange, rangeGeq,
                              rangeLimit, rangeOffset, rangeRequested,
                              restrictRange)
 import PostgREST.Types
-import Protolude            hiding (head)
+import Protolude            hiding (head, toS)
+import Protolude.Conv       (toS)
 
 type RequestBody = BL.ByteString
 
diff --git a/src/PostgREST/App.hs b/src/PostgREST/App.hs
index 88a2feef6..a0f2ae9a0 100644
--- a/src/PostgREST/App.hs
+++ b/src/PostgREST/App.hs
@@ -64,7 +64,8 @@ import PostgREST.Statements       (callProcStatement,
                                    createReadStatement,
                                    createWriteStatement)
 import PostgREST.Types
-import Protolude                  hiding (Proxy, intercalate)
+import Protolude                  hiding (Proxy, intercalate, toS)
+import Protolude.Conv             (toS)
 
 postgrest :: AppConfig -> IORef (Maybe DbStructure) -> P.Pool -> IO UTCTime -> IO () -> Application
 postgrest conf refDbStructure pool getTime worker =
@@ -180,7 +181,7 @@ app dbStructure proc cols conf apiRequest =
                         , Just $ contentRangeH 1 0 $ if shouldCount then Just queryTotal else Nothing
                         , if null pkCols && isNothing (iOnConflict apiRequest)
                             then Nothing
-                            else (\x -> ("Preference-Applied", show x)) <$> iPreferResolution apiRequest
+                            else (\x -> ("Preference-Applied", encodeUtf8 (show x))) <$> iPreferResolution apiRequest
                         ] ++ ctHeaders)) (unwrapGucHeader <$> ghdrs)
                   if contentType == CTSingularJSON && queryTotal /= 1
                     then do
diff --git a/src/PostgREST/Auth.hs b/src/PostgREST/Auth.hs
index 4524cec90..8f16b3aaa 100644
--- a/src/PostgREST/Auth.hs
+++ b/src/PostgREST/Auth.hs
@@ -31,7 +31,8 @@ import Control.Lens.Operators
 import Crypto.JWT
 
 import PostgREST.Types
-import Protolude
+import Protolude       hiding (toS)
+import Protolude.Conv  (toS)
 
 {-|
   Possible situations encountered with client JWTs
diff --git a/src/PostgREST/Config.hs b/src/PostgREST/Config.hs
index cfaec4e55..9b38fec83 100644
--- a/src/PostgREST/Config.hs
+++ b/src/PostgREST/Config.hs
@@ -32,7 +32,6 @@ import qualified Data.CaseInsensitive         as CI
 import qualified Data.Configurator            as C
 import qualified Text.PrettyPrint.ANSI.Leijen as L
 
-import Control.Exception           (Handler (..))
 import Control.Lens                (preview)
 import Control.Monad               (fail)
 import Crypto.JWT                  (StringOrURI, stringOrUri)
@@ -62,8 +61,8 @@ import PostgREST.Error   (ApiRequestError (..))
 import PostgREST.Parsers (pRoleClaimKey)
 import PostgREST.Types   (JSPath, JSPathExp (..))
 import Protolude         hiding (concat, hPutStrLn, intercalate, null,
-                          take, (<>))
-
+                          take, toS, (<>))
+import Protolude.Conv    (toS)
 
 
 -- | Config file settings for the server
diff --git a/src/PostgREST/DbStructure.hs b/src/PostgREST/DbStructure.hs
index f3cadf1a4..720d157cf 100644
--- a/src/PostgREST/DbStructure.hs
+++ b/src/PostgREST/DbStructure.hs
@@ -35,14 +35,13 @@ import Data.Set                      as S (fromList)
 import Data.Text                     (breakOn, dropAround, split,
                                       splitOn, strip)
 import GHC.Exts                      (groupWith)
+import Protolude                     hiding (toS)
+import Protolude.Conv                (toS)
+import Protolude.Unsafe              (unsafeHead)
 import Text.InterpolatedString.Perl6 (q, qc)
-import Unsafe                        (unsafeHead)
-
-import Control.Applicative
 
 import PostgREST.Private.Common
 import PostgREST.Types
-import Protolude
 
 getDbStructure :: [Schema] -> PgVersion -> HT.Transaction DbStructure
 getDbStructure schemas pgVer = do
diff --git a/src/PostgREST/Error.hs b/src/PostgREST/Error.hs
index 9766b1924..51c0c177f 100644
--- a/src/PostgREST/Error.hs
+++ b/src/PostgREST/Error.hs
@@ -27,7 +27,8 @@ import Network.Wai (Response, responseLBS)
 import Network.HTTP.Types.Header
 
 import PostgREST.Types
-import Protolude
+import Protolude       hiding (toS)
+import Protolude.Conv  (toS)
 
 
 class (JSON.ToJSON a) => PgrstError a where
@@ -279,7 +280,7 @@ instance JSON.ToJSON SimpleError where
 
 invalidTokenHeader :: Text -> Header
 invalidTokenHeader m =
-  ("WWW-Authenticate", "Bearer error=\"invalid_token\", " <> "error_description=" <> show m)
+  ("WWW-Authenticate", "Bearer error=\"invalid_token\", " <> "error_description=" <> encodeUtf8 (show m))
 
 singularityError :: (Integral a) => a -> SimpleError
 singularityError = SingularityError . toInteger
diff --git a/src/PostgREST/Middleware.hs b/src/PostgREST/Middleware.hs
index 93d3e4ec2..73bcd5bb6 100644
--- a/src/PostgREST/Middleware.hs
+++ b/src/PostgREST/Middleware.hs
@@ -27,7 +27,8 @@ import PostgREST.Config       (AppConfig (..), corsPolicy)
 import PostgREST.Error        (SimpleError (JwtTokenInvalid, JwtTokenMissing),
                                errorResponseFor)
 import PostgREST.QueryBuilder (setLocalQuery, setLocalSearchPathQuery)
-import Protolude              hiding (head)
+import Protolude              hiding (head, toS)
+import Protolude.Conv         (toS)
 
 runWithClaims :: AppConfig -> JWTAttempt ->
                  (ApiRequest -> H.Transaction Response) ->
diff --git a/src/PostgREST/OpenAPI.hs b/src/PostgREST/OpenAPI.hs
index 4dc497132..f98978271 100644
--- a/src/PostgREST/OpenAPI.hs
+++ b/src/PostgREST/OpenAPI.hs
@@ -32,7 +32,8 @@ import PostgREST.Types      (Column (..), ForeignKey (..), PgArg (..),
                              PrimaryKey (..), ProcDescription (..),
                              Proxy (..), Table (..), toMime)
 import Protolude            hiding (Proxy, dropWhile, get,
-                             intercalate, (&))
+                             intercalate, toLower, toS, (&))
+import Protolude.Conv       (toS)
 
 makeMimeList :: [ContentType] -> MimeList
 makeMimeList cs = MimeList $ map (fromString . toS . toMime) cs
diff --git a/src/PostgREST/Parsers.hs b/src/PostgREST/Parsers.hs
index 98239f8e5..12a989e32 100644
--- a/src/PostgREST/Parsers.hs
+++ b/src/PostgREST/Parsers.hs
@@ -22,7 +22,9 @@ import Text.ParserCombinators.Parsec hiding (many, (<|>))
 import PostgREST.Error      (ApiRequestError (ParseRequestError))
 import PostgREST.RangeQuery (NonnegRange)
 import PostgREST.Types
-import Protolude            hiding (intercalate, option, replace, try)
+import Protolude            hiding (intercalate, option, replace, toS,
+                             try)
+import Protolude.Conv       (toS)
 
 pRequestSelect :: Text -> Either ApiRequestError [Tree SelectItem]
 pRequestSelect selStr =
diff --git a/src/PostgREST/Private/QueryFragment.hs b/src/PostgREST/Private/QueryFragment.hs
index cbd5a868e..95d54edb1 100644
--- a/src/PostgREST/Private/QueryFragment.hs
+++ b/src/PostgREST/Private/QueryFragment.hs
@@ -16,7 +16,8 @@ import qualified Data.Text                     as T (map, null,
                                                      takeWhile)
 import           PostgREST.Types
 import           Protolude                     hiding (cast,
-                                                intercalate, replace)
+                                                intercalate, replace,
+                                                toLower)
 import           Text.InterpolatedString.Perl6 (qc)
 
 noLocationF :: SqlFragment
diff --git a/src/PostgREST/RangeQuery.hs b/src/PostgREST/RangeQuery.hs
index 0aadafeb1..0cb02a489 100644
--- a/src/PostgREST/RangeQuery.hs
+++ b/src/PostgREST/RangeQuery.hs
@@ -26,7 +26,8 @@ import Data.Ranged.Ranges
 import Network.HTTP.Types.Header
 import Network.HTTP.Types.Status
 
-import Protolude
+import Protolude      hiding (toS)
+import Protolude.Conv (toS)
 
 type NonnegRange = Range Integer
 
@@ -91,9 +92,9 @@ rangeStatusHeader topLevelRange queryTotal tableTotal =
 
 contentRangeH :: (Integral a, Show a) => a -> a -> Maybe a -> Header
 contentRangeH lower upper total =
-    ("Content-Range", headerValue)
+    ("Content-Range", toUtf8 headerValue)
     where
-      headerValue   = rangeString <> "/" <> totalString
+      headerValue   = rangeString <> "/" <> totalString :: Text
       rangeString
         | totalNotZero && fromInRange = show lower <> "-" <> show upper
         | otherwise = "*"
diff --git a/src/PostgREST/Statements.hs b/src/PostgREST/Statements.hs
index b169f537d..056f39190 100644
--- a/src/PostgREST/Statements.hs
+++ b/src/PostgREST/Statements.hs
@@ -29,7 +29,8 @@ import           PostgREST.Private.Common
 import           PostgREST.Private.QueryFragment
 import           PostgREST.Types
 import           Protolude                       hiding (cast,
-                                                  replace)
+                                                  replace, toS)
+import           Protolude.Conv                  (toS)
 import           Text.InterpolatedString.Perl6   (qc)
 
 {-| The generic query result format used by API responses. The location header
diff --git a/src/PostgREST/Types.hs b/src/PostgREST/Types.hs
index 9cdd54750..33e13906f 100644
--- a/src/PostgREST/Types.hs
+++ b/src/PostgREST/Types.hs
@@ -24,7 +24,8 @@ import Network.HTTP.Types.Header (Header, hContentType)
 import Data.Tree
 
 import PostgREST.RangeQuery (NonnegRange)
-import Protolude
+import Protolude            hiding (toS)
+import Protolude.Conv       (toS)
 
 -- | Enumeration of currently supported response content types
 data ContentType = CTApplicationJSON | CTSingularJSON
diff --git a/stack.yaml b/stack.yaml
index 99140ca17..fdcdedd85 100644
--- a/stack.yaml
+++ b/stack.yaml
@@ -16,3 +16,4 @@ extra-deps:
 - configurator-pg-0.2.2@sha256:8f3f7c66dd4a53852283c70806ebc101a7219f8b01c3e80c5130e9749c998dc8,2987
 - hspec-wai-json-0.10.1@sha256:67b405c38f0a9e2771480c8d3ecd8aeb8d8776a35d3b2906cb1b76c9538617e4,1629
 - interpolatedstring-perl6-1.0.2@sha256:7ce49c8a69a2a1b89c001ed79db2aab656ffd0faf2a7a701a553b6deb5c8ba7f,1073
+- protolude-0.3.0@sha256:8361b811b420585b122a7ba715aa5923834db6e8c36309bf267df2dbf66b95ef,2693
diff --git a/stack.yaml.lock b/stack.yaml.lock
index 04648b38e..cc4d05a75 100644
--- a/stack.yaml.lock
+++ b/stack.yaml.lock
@@ -25,6 +25,13 @@ packages:
       sha256: f7f0b06c58db814d1f12ed6f4f4cb67ff8c72e51da61c04db12c2aedb896542e
   original:
     hackage: interpolatedstring-perl6-1.0.2@sha256:7ce49c8a69a2a1b89c001ed79db2aab656ffd0faf2a7a701a553b6deb5c8ba7f,1073
+- completed:
+    hackage: protolude-0.3.0@sha256:8361b811b420585b122a7ba715aa5923834db6e8c36309bf267df2dbf66b95ef,2693
+    pantry-tree:
+      size: 1644
+      sha256: babf32b414f25f790b7a4ce6bae5c960bc51a11a289e7c47335b222e6762560c
+  original:
+    hackage: protolude-0.3.0
 snapshots:
 - completed:
     size: 492015
diff --git a/test/Main.hs b/test/Main.hs
index 869f6a667..d713942b4 100644
--- a/test/Main.hs
+++ b/test/Main.hs
@@ -16,7 +16,8 @@ import PostgREST.App         (postgrest)
 import PostgREST.Config      (AppConfig (..))
 import PostgREST.DbStructure (getDbStructure, getPgVersion)
 import PostgREST.Types       (pgVersion95, pgVersion96)
-import Protolude             hiding (toList)
+import Protolude             hiding (toList, toS)
+import Protolude.Conv        (toS)
 import SpecHelper
 
 import qualified Feature.AndOrParamsSpec
diff --git a/test/QueryCost.hs b/test/QueryCost.hs
index 81c5860be..2ef2a756c 100644
--- a/test/QueryCost.hs
+++ b/test/QueryCost.hs
@@ -10,7 +10,8 @@ import qualified Hasql.Transaction          as HT
 import qualified Hasql.Transaction.Sessions as HT
 import           Text.Heredoc
 
-import Protolude hiding (get)
+import Protolude      hiding (get, toS)
+import Protolude.Conv (toS)
 
 import PostgREST.QueryBuilder (requestToCallProcQuery)
 import PostgREST.Types
diff --git a/test/SpecHelper.hs b/test/SpecHelper.hs
index 00eeb14bb..41ad4659e 100644
--- a/test/SpecHelper.hs
+++ b/test/SpecHelper.hs
@@ -24,7 +24,8 @@ import Text.Heredoc
 
 import PostgREST.Config (AppConfig (..))
 import PostgREST.Types  (JSPathExp (..))
-import Protolude
+import Protolude        hiding (toS)
+import Protolude.Conv   (toS)
 
 matchContentTypeJson :: MatchHeader
 matchContentTypeJson = "Content-Type" <:> "application/json; charset=utf-8"