diff --git a/Hack/Middleware/CleanPath.hs b/Hack/Middleware/CleanPath.hs
index 71c6973e..0fc1d82c 100644
--- a/Hack/Middleware/CleanPath.hs
+++ b/Hack/Middleware/CleanPath.hs
@@ -33,7 +33,7 @@ splitPath :: String -> Either String [String]
 splitPath s =
     let corrected = ats $ rds s
      in if corrected == s
-            then Right $ map decodeUrl $ filter (\l -> length l /= 0)
+            then Right $ map decodeUrl $ filter (not . null)
                        $ splitOneOf "/" s
             else Left corrected
 
diff --git a/Hack/Middleware/ClientSession.hs b/Hack/Middleware/ClientSession.hs
index 76a9f8cb..963fffe2 100644
--- a/Hack/Middleware/ClientSession.hs
+++ b/Hack/Middleware/ClientSession.hs
@@ -76,7 +76,7 @@ clientsession cnames key app env = do
         twentyMinutes = 20 * 60
     let exp = fromIntegral twentyMinutes `addUTCTime` now
     let formattedExp = formatTime defaultTimeLocale "%a, %d-%b-%Y %X %Z" exp
-    let oldCookies = filter (\(k, _) -> not $ k `elem` map fst interceptHeaders) convertedCookies
+    let oldCookies = filter (\(k, _) -> k `notElem` map fst interceptHeaders) convertedCookies
     let newCookies = map (setCookie key exp formattedExp remoteHost') $
                      oldCookies ++ interceptHeaders
     let res' = res { headers = newCookies ++ headers' }
diff --git a/Yesod.hs b/Yesod.hs
index 6d492102..124c83d4 100644
--- a/Yesod.hs
+++ b/Yesod.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE TemplateHaskell #-}
 ---------------------------------------------------------
 --
 -- Module        : Yesod
diff --git a/Yesod/Handler.hs b/Yesod/Handler.hs
index 50d2ff16..4b997079 100644
--- a/Yesod/Handler.hs
+++ b/Yesod/Handler.hs
@@ -65,8 +65,8 @@ instance Monad (Handler yesod) where
         (headers, c) <- handler rr
         (headers', c') <-
             case c of
-                (HCError e) -> return $ ([], HCError e)
-                (HCSpecial e) -> return $ ([], HCSpecial e)
+                (HCError e) -> return ([], HCError e)
+                (HCSpecial e) -> return ([], HCSpecial e)
                 (HCContent a) -> unHandler (f a) rr
         return (headers ++ headers', c')
 instance MonadIO (Handler yesod) where
diff --git a/Yesod/Helpers/Auth.hs b/Yesod/Helpers/Auth.hs
index 96229ce6..e443ab18 100644
--- a/Yesod/Helpers/Auth.hs
+++ b/Yesod/Helpers/Auth.hs
@@ -37,7 +37,6 @@ import Control.Monad.Reader
 import Control.Monad.Attempt
 
 import Data.Maybe (fromMaybe)
-import Control.Monad.Attempt
 
 data AuthResource =
     Check
diff --git a/Yesod/Rep.hs b/Yesod/Rep.hs
index ae5e4998..02952ca6 100644
--- a/Yesod/Rep.hs
+++ b/Yesod/Rep.hs
@@ -44,7 +44,8 @@ module Yesod.Rep
 
 import Data.ByteString.Lazy (ByteString)
 import Data.Text.Lazy (Text)
-import Data.Maybe (catMaybes)
+import Data.Maybe (mapMaybe)
+import Data.Function (on)
 
 #if TEST
 import Data.Object.Html hiding (testSuite)
@@ -93,7 +94,7 @@ instance Show ContentType where
     show TypeOctet = "application/octet-stream"
     show (TypeOther s) = s
 instance Eq ContentType where
-    x == y = show x == show y
+    (==) = (==) `on` show
 
 newtype Content = Content { unContent :: ByteString }
     deriving (Eq, Show)
@@ -115,7 +116,7 @@ class HasReps a where
     chooseRep :: a -> RepChooser
     chooseRep a ts = do
       let (ct, c) =
-            case catMaybes $ map helper ts of
+            case mapMaybe helper ts of
                 (x:_) -> x
                 [] -> case reps of
                         [] -> error "Empty reps"
diff --git a/Yesod/Request.hs b/Yesod/Request.hs
index 515f0388..e8263a74 100644
--- a/Yesod/Request.hs
+++ b/Yesod/Request.hs
@@ -1,6 +1,7 @@
 {-# LANGUAGE FlexibleInstances #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverlappingInstances #-} -- Parameter String
+{-# LANGUAGE TypeSynonymInstances #-}
 ---------------------------------------------------------
 --
 -- Module        : Yesod.Request
@@ -274,7 +275,7 @@ instance Parameter a => Parameter [a] where
                 Left l -> Left l
                 Right rest' -> Right $ r : rest'
 
-instance Parameter [Char] where
+instance Parameter String where
     readParam = Right . paramValue
 
 instance Parameter Int where