diff --git a/src/Network/Wai/Middleware/ContentType.hs b/src/Network/Wai/Middleware/ContentType.hs
--- a/src/Network/Wai/Middleware/ContentType.hs
+++ b/src/Network/Wai/Middleware/ContentType.hs
@@ -35,6 +35,7 @@
 
 type AcceptHeader = BS.ByteString
 
+-- | Turn a map of content types to middlewares, into a middleware.
 fileExtsToMiddleware :: MonadIO m =>
                         FileExtListenerT (MiddlewareT m) m ()
                      -> MiddlewareT m
@@ -46,7 +47,8 @@
     m <- mMiddleware
     return $ m app req respond
 
-
+-- | Given an HTTP @Accept@ header and a content type to base lookups off of, and
+-- a map of responses, find a response.
 lookupResponse :: Monad m =>
                   Maybe AcceptHeader
                -> FileExt
diff --git a/src/Network/Wai/Middleware/ContentType/Builder.hs b/src/Network/Wai/Middleware/ContentType/Builder.hs
--- a/src/Network/Wai/Middleware/ContentType/Builder.hs
+++ b/src/Network/Wai/Middleware/ContentType/Builder.hs
@@ -35,7 +35,7 @@
 builderStatusWith f e s hs i =
   let r = builderOnlyStatus s hs i in
   FileExtListenerT $ tell $
-    FileExts $ Map.singleton e $ \_ _ respond -> liftIO $ respond $ f r
+    FileExts $ Map.singleton e $ \_ _ respond -> respond (f r)
 
 
 
diff --git a/src/Network/Wai/Middleware/ContentType/ByteString.hs b/src/Network/Wai/Middleware/ContentType/ByteString.hs
--- a/src/Network/Wai/Middleware/ContentType/ByteString.hs
+++ b/src/Network/Wai/Middleware/ContentType/ByteString.hs
@@ -38,7 +38,7 @@
                      -> FileExtListenerT (MiddlewareT m) m ()
 bytestringStatusWith f fe s hs i = do
   r <- lift $ U.bytestring s hs i
-  middleware fe $ \_ _ respond -> liftIO $ respond $ f r
+  middleware fe $ \_ _ respond -> respond (f r)
 
 
 -- * Raw @Response@s
diff --git a/wai-middleware-content-type.cabal b/wai-middleware-content-type.cabal
--- a/wai-middleware-content-type.cabal
+++ b/wai-middleware-content-type.cabal
@@ -1,5 +1,5 @@
 Name:                   wai-middleware-content-type
-Version:                0.0.3
+Version:                0.0.3.1
 Author:                 Athan Clark <athan.clark@gmail.com>
 Maintainer:             Athan Clark <athan.clark@gmail.com>
 License:                BSD3
@@ -41,7 +41,7 @@
                       , text
                       , transformers
                       , wai
-                      , wai-transformers
+                      , wai-transformers >= 0.0.3
                       , wai-util
 
 Source-Repository head