diff --git a/servant-hmac-auth.cabal b/servant-hmac-auth.cabal
--- a/servant-hmac-auth.cabal
+++ b/servant-hmac-auth.cabal
@@ -1,6 +1,6 @@
 cabal-version:       2.4
 name:                servant-hmac-auth
-version:             0.1.3
+version:             0.1.4
 synopsis:            Servant authentication with HMAC
 description:         Servant authentication with HMAC. See README.md for usage example.
 homepage:            https://github.com/holmusk/servant-hmac-auth
@@ -15,7 +15,8 @@
 extra-source-files:  README.md
                    , CHANGELOG.md
 tested-with:         GHC == 8.6.5
-                     GHC == 8.8.3
+                     GHC == 8.8.4
+                     GHC == 8.10.7
 
 source-repository head
   type:                git
@@ -64,7 +65,7 @@
                            Servant.Auth.Hmac.Client
                            Servant.Auth.Hmac.Server
 
-  build-depends:       base64-bytestring ^>= 1.0
+  build-depends:       base64-bytestring >= 1.0 && <= 2
                      , binary ^>= 0.8
                      , bytestring ^>= 0.10
                      , case-insensitive ^>= 1.2
@@ -74,10 +75,10 @@
                      , http-client >= 0.6.4 && < 0.8
                      , memory >= 0.15 && < 0.17
                      , mtl ^>= 2.2.2
-                     , servant ^>= 0.18
-                     , servant-client ^>= 0.18
-                     , servant-client-core ^>= 0.18
-                     , servant-server ^>= 0.18
+                     , servant ^>= 0.18 || ^>= 0.19
+                     , servant-client ^>= 0.18 || ^>= 0.19
+                     , servant-client-core ^>= 0.18 || ^>= 0.19
+                     , servant-server ^>= 0.18 || ^>= 0.19
                      , transformers ^>= 0.5
                      , wai ^>= 3.2.2.1
 
@@ -88,3 +89,11 @@
   main-is:             Spec.hs
   ghc-options:         -threaded -rtsopts -with-rtsopts=-N
   build-depends:       servant-hmac-auth
+                     , case-insensitive ^>= 1.2
+                     , filepath
+                     , hspec
+                     , hspec-golden ^>= 0.2
+                     , http-types ^>= 0.12
+                     , text
+  other-modules:       Servant.Auth.Hmac.CryptoSpec
+  build-tool-depends:  hspec-discover:hspec-discover == 2.*
diff --git a/src/Servant/Auth/Hmac/Client.hs b/src/Servant/Auth/Hmac/Client.hs
--- a/src/Servant/Auth/Hmac/Client.hs
+++ b/src/Servant/Auth/Hmac/Client.hs
@@ -20,10 +20,12 @@
 import Control.Monad.Reader (MonadReader (..), ReaderT, asks, runReaderT)
 import Control.Monad.Trans.Class (lift)
 import Data.ByteString (ByteString)
+import Data.CaseInsensitive (mk)
 import Data.Foldable (toList)
 import Data.List (sort)
 import Data.Proxy (Proxy (..))
 import Data.Sequence (fromList, (<|))
+import Data.String (fromString)
 import Servant.Client (BaseUrl, Client, ClientEnv (baseUrl), ClientError, ClientM, HasClient,
                        runClientM)
 import Servant.Client.Core (RunClient (..), clientIn)
@@ -109,11 +111,11 @@
     { rpMethod  = Client.method req
     , rpContent = "" -- toBsBody $ Client.requestBody req
     , rpHeaders = keepWhitelistedHeaders
-                $ ("Host", host)
+                $ ("Host", hostAndPort)
                 : ("Accept-Encoding", "gzip")
                 : Client.requestHeaders req
 
-    , rpRawUrl  = host <> Client.path req <> Client.queryString req
+    , rpRawUrl  = hostAndPort <> Client.path req <> Client.queryString req
     }
   where
     req :: Client.Request
@@ -122,8 +124,14 @@
              fromList $ sort $ toList $ Servant.requestQueryString sreq
         }
 
-    host :: ByteString
-    host = Client.host req
+    hostAndPort :: ByteString
+    hostAndPort = case lookup (mk "Host") (Client.requestHeaders req) of
+        Just hp -> hp
+        Nothing ->
+            case (Client.secure req, Client.port req) of
+                (True, 443) -> Client.host req
+                (False, 80) -> Client.host req
+                (_, p) -> Client.host req <> ":" <> fromString (show p)
 
 --    toBsBody :: RequestBody -> ByteString
 --    toBsBody (RequestBodyBS bs)       = bs
diff --git a/test/Servant/Auth/Hmac/CryptoSpec.hs b/test/Servant/Auth/Hmac/CryptoSpec.hs
new file mode 100644
--- /dev/null
+++ b/test/Servant/Auth/Hmac/CryptoSpec.hs
@@ -0,0 +1,45 @@
+{-# LANGUAGE TemplateHaskellQuotes #-}
+
+module Servant.Auth.Hmac.CryptoSpec (spec) where
+
+import Data.CaseInsensitive
+import Data.Text (Text)
+import qualified Data.Text as Text
+import qualified Data.Text.Encoding as TE
+import qualified Data.Text.IO as TIO
+import Network.HTTP.Types
+import Servant.Auth.Hmac.Crypto (RequestPayload (..), SecretKey (..), Signature (..), requestSignature, signSHA256)
+import System.FilePath
+import Test.Hspec
+import Test.Hspec.Golden
+
+goldenTest :: String -> Text -> Golden Text
+goldenTest name actualOutput =
+    Golden
+        { output = actualOutput
+        , encodePretty = Text.unpack
+        , writeToFile = TIO.writeFile
+        , readFromFile = TIO.readFile
+        , goldenFile = ".golden" </> name </> "golden"
+        , actualFile = Just (".golden" </> name </> "actual")
+        , failFirstTime = False
+        }
+
+sha256Scenarios :: [(SecretKey, RequestPayload)]
+sha256Scenarios =
+    [ (SecretKey "Some-s3cr3t", RequestPayload methodGet "" [(mk "Host", "my-server.local")] "my-server.local/test")
+    , (SecretKey "s3cret2!", RequestPayload methodPost "This is a text content." [(mk "Host", "www.haskell.server"), (mk "Authentication", "Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==")] "www.haskell.server/test")
+    , (SecretKey "123456789abcdef", RequestPayload methodPatch "\00HellowORLD" [(mk "Host", "files.myrepository.org"), (mk "Accept-Encoding", "gzip")] "files.myrepository.org/files/4601237722")
+    ]
+
+formatResponse :: [Signature] -> Text
+formatResponse = Text.unlines . fmap (TE.decodeLatin1 . unSignature)
+
+spec :: Spec
+spec =
+    describe "requestSignature" $
+        context "when using SHA256 for signature" $
+            it "should compute the request's signature" $
+                let signatures = uncurry (requestSignature signSHA256) <$> sha256Scenarios
+                    actualOutput = formatResponse signatures
+                 in goldenTest (show 'requestSignature) actualOutput
diff --git a/test/Spec.hs b/test/Spec.hs
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -1,3 +1,1 @@
-main :: IO ()
-main = putStrLn ("Test suite not yet implemented" :: String)
-
+{-# OPTIONS_GHC -F -pgmF hspec-discover #-}