diff --git a/Network/Wai/Middleware/RequestLogger.hs b/Network/Wai/Middleware/RequestLogger.hs
--- a/Network/Wai/Middleware/RequestLogger.hs
+++ b/Network/Wai/Middleware/RequestLogger.hs
@@ -81,7 +81,7 @@
 mkRequestLogger RequestLoggerSettings{..} = do
     callback <-
         case destination of
-            Handle h -> return $ BS.hPutStr h . toByteString . logStrBuilder
+            Handle h -> return $ BS.hPutStr h . logToByteString
             Logger l -> return $ pushLogStr l
             Callback c -> return c
     case outputFormat of
diff --git a/Network/Wai/Middleware/RequestLogger/Internal.hs b/Network/Wai/Middleware/RequestLogger/Internal.hs
--- a/Network/Wai/Middleware/RequestLogger/Internal.hs
+++ b/Network/Wai/Middleware/RequestLogger/Internal.hs
@@ -4,12 +4,22 @@
 -- https://github.com/yesodweb/wai/issues/192
 module Network.Wai.Middleware.RequestLogger.Internal
     ( module Network.Wai.Middleware.RequestLogger.Internal
-    , toByteString
+    , logToByteString
     ) where
 
 import Data.ByteString (ByteString)
 import Network.Wai.Logger (clockDateCacher)
 
+#if MIN_VERSION_fast_logger(2, 1, 0)
+import System.Log.FastLogger (LogStr, fromLogStr)
+
+logToByteString :: LogStr -> ByteString
+logToByteString = fromLogStr
+
+#else
+
+import System.Log.FastLogger (LogStr, logStrBuilder)
+
 #if MIN_VERSION_bytestring(0, 10, 2)
 import Data.ByteString.Builder (toLazyByteString, Builder)
 import qualified Data.ByteString.Lazy as L
@@ -19,6 +29,11 @@
 
 #else
 import Blaze.ByteString.Builder (toByteString)
+#endif
+
+logToByteString :: LogStr -> ByteString
+logToByteString = toByteString . logStrBuilder
+
 #endif
 
 getDateGetter :: IO (IO ByteString)
diff --git a/test/WaiExtraTest.hs b/test/WaiExtraTest.hs
--- a/test/WaiExtraTest.hs
+++ b/test/WaiExtraTest.hs
@@ -557,7 +557,7 @@
       where
         output = TE.encodeUtf8 $ T.toStrict output'
 
-        logToBs = toByteString . logStrBuilder
+        logToBs = fromLogStr
 
     {-debugApp = debug $ \req -> do-}
         {-return $ responseLBS status200 [ ] ""-}
diff --git a/wai-extra.cabal b/wai-extra.cabal
--- a/wai-extra.cabal
+++ b/wai-extra.cabal
@@ -1,5 +1,5 @@
 Name:                wai-extra
-Version:             2.0.1.1
+Version:             2.0.1.2
 Synopsis:            Provides some basic WAI handlers and middleware.
 Description:         The goal here is to provide common features without many dependencies.
 License:             MIT
@@ -33,8 +33,8 @@
                    , text                      >= 0.7
                    , case-insensitive          >= 0.2
                    , data-default
-                   , fast-logger               >= 2.0      && < 2.1
-                   , wai-logger                >= 2.0      && < 2.1
+                   , fast-logger               >= 2.0      && < 2.2
+                   , wai-logger                >= 2.0      && < 2.2
                    , conduit                   >= 1.0      && < 1.1
                    , zlib-conduit              >= 0.5      && < 1.1
                    , blaze-builder-conduit     >= 0.5      && < 1.1
@@ -86,7 +86,7 @@
                    , blaze-builder             >= 0.2.1.4  && < 0.4
                    , data-default
                    , conduit
-                   , fast-logger
+                   , fast-logger               >= 2.1
                    , resourcet
     ghc-options:       -Wall