diff --git a/happstack-server.cabal b/happstack-server.cabal
--- a/happstack-server.cabal
+++ b/happstack-server.cabal
@@ -1,5 +1,5 @@
 Name:                happstack-server
-Version:             0.5.0.2
+Version:             0.5.0.3
 Synopsis:            Web related tools and services.
 Description:         Web framework
 License:             BSD3
@@ -69,13 +69,13 @@
                        happstack-util >= 0.5 && < 0.6,
                        html,
                        MaybeT,
-                       mtl,
+                       mtl >= 1.1 && < 2.1,
                        network,
                        old-locale,
                        old-time,
                        parsec < 4,
                        process,
-                       sendfile >= 0.6.1 && < 0.7,
+                       sendfile >= 0.6.1 && < 0.8,
                        template-haskell,
                        time,
                        utf8-string >= 0.3.4 && < 0.4,
diff --git a/src/Happstack/Server/HTTP/Handler.hs b/src/Happstack/Server/HTTP/Handler.hs
--- a/src/Happstack/Server/HTTP/Handler.hs
+++ b/src/Happstack/Server/HTTP/Handler.hs
@@ -361,5 +361,5 @@
 responseMessage 503 = P.pack " 503 Service Unavailable\r\n"
 responseMessage 504 = P.pack " 504 Gateway Time-out\r\n"
 responseMessage 505 = P.pack " 505 HTTP Version not supported\r\n"
-responseMessage x   = P.pack (show x ++ "\r\n")
+responseMessage x   = P.pack (" " ++ show x ++ " \r\n")
 
diff --git a/src/Happstack/Server/SimpleHTTP.hs b/src/Happstack/Server/SimpleHTTP.hs
--- a/src/Happstack/Server/SimpleHTTP.hs
+++ b/src/Happstack/Server/SimpleHTTP.hs
@@ -575,7 +575,7 @@
 instance (Monad m) => FilterMonad Response (WebT m) where
     setFilter f = WebT $ lift $ setFilter $ f
     composeFilter f = WebT . lift . composeFilter $ f
-    getFilter     m = WebT $ ErrorT $ fmap lft $ getFilter (runErrorT $ unWebT m)
+    getFilter     m = WebT $ ErrorT $ liftM lft $ getFilter (runErrorT $ unWebT m)
         where
           lft (Left  r, _) = Left r
           lft (Right a, f) = Right (a, f)