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
@@ -53,11 +53,13 @@
 -- a map of responses, find a response.
 lookupFileExt :: Maybe AcceptHeader
               -> Maybe FileExt
-              -> FileExtMap r
-              -> Maybe r
-lookupFileExt mAcceptBS mFe fexts =
-  getFirst . foldMap (First . flip HM.lookup fexts) . findFE $
-    maybe allFileExts possibleFileExts mAcceptBS
+              -> FileExtMap
+              -> Maybe Response
+lookupFileExt mAcceptBS mFe map =
+    getFirst
+  . foldMap (\fe -> First $ runResponseVia <$> HM.lookup fe map)
+  . findFE
+  $ maybe allFileExts possibleFileExts mAcceptBS
   where
     findFE :: [FileExt] -> [FileExt]
     findFE xs =
@@ -65,7 +67,7 @@
         Nothing -> xs
         Just fe -> fe <$ guard (fe `elem` xs)
 
-fileExtsToMiddleware :: Monad m => FileExtListenerT Response m a -> MiddlewareT m
+fileExtsToMiddleware :: Monad m => FileExtListenerT m a -> MiddlewareT m
 fileExtsToMiddleware xs app req respond = do
   map <- execFileExtListenerT xs
   let mAcceptHeader = lookup "Accept" (requestHeaders req)
diff --git a/src/Network/Wai/Middleware/ContentType/Blaze.hs b/src/Network/Wai/Middleware/ContentType/Blaze.hs
--- a/src/Network/Wai/Middleware/ContentType/Blaze.hs
+++ b/src/Network/Wai/Middleware/ContentType/Blaze.hs
@@ -1,7 +1,11 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
 module Network.Wai.Middleware.ContentType.Blaze where
 
 import           Network.Wai.Middleware.ContentType.Types
-import           Network.HTTP.Types                      (Status, ResponseHeaders)
+import           Network.HTTP.Types                      (status200, Status, ResponseHeaders)
 import           Network.Wai                             (Response, responseBuilder)
 
 import qualified Text.Blaze.Html                         as H
@@ -13,9 +17,14 @@
 
 blaze :: Monad m =>
          H.Html
-      -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+      -> FileExtListenerT m ()
 blaze i =
-  tell' $ HM.singleton Html (blazeOnly i)
+  tell' $ HM.singleton Html $
+    ResponseVia
+      i
+      status200
+      [("Content-Type", "text/html")]
+      blazeOnly
 
 {-# INLINEABLE blaze #-}
 
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
@@ -1,7 +1,7 @@
 module Network.Wai.Middleware.ContentType.ByteString where
 
 import           Network.Wai.Middleware.ContentType.Types
-import           Network.HTTP.Types                      (Status, ResponseHeaders)
+import           Network.HTTP.Types                      (status200, Status, ResponseHeaders)
 import           Network.Wai                             (Response, responseLBS)
 
 import qualified Data.ByteString.Lazy                    as LBS
@@ -14,9 +14,14 @@
 bytestring :: Monad m =>
               FileExt
            -> LBS.ByteString
-           -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+           -> FileExtListenerT m ()
 bytestring fe i =
-  tell' $ HM.singleton fe (bytestringOnly i)
+  tell' $ HM.singleton fe $
+    ResponseVia
+      i
+      status200
+      []
+      bytestringOnly
 
 {-# INLINEABLE bytestring #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Cassius.hs b/src/Network/Wai/Middleware/ContentType/Cassius.hs
--- a/src/Network/Wai/Middleware/ContentType/Cassius.hs
+++ b/src/Network/Wai/Middleware/ContentType/Cassius.hs
@@ -1,8 +1,13 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
+
 module Network.Wai.Middleware.ContentType.Cassius where
 
 import           Network.Wai.Middleware.ContentType.Types as CT
 import           Network.Wai.Middleware.ContentType.Text
-import           Network.HTTP.Types                       (Status, ResponseHeaders)
+import           Network.HTTP.Types                       (status200, Status, ResponseHeaders)
 import           Network.Wai                              (Response)
 
 import           Text.Cassius
@@ -13,9 +18,14 @@
 
 cassius :: Monad m =>
            Css
-        -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+        -> FileExtListenerT m ()
 cassius i =
-  tell' $ HM.singleton CT.Css (cassiusOnly i)
+  tell' $ HM.singleton CT.Css $
+    ResponseVia
+      i
+      status200
+      [("Content-Type", "text/css")]
+      cassiusOnly
 
 {-# INLINEABLE cassius #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Clay.hs b/src/Network/Wai/Middleware/ContentType/Clay.hs
--- a/src/Network/Wai/Middleware/ContentType/Clay.hs
+++ b/src/Network/Wai/Middleware/ContentType/Clay.hs
@@ -1,8 +1,13 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
+
 module Network.Wai.Middleware.ContentType.Clay where
 
 import           Network.Wai.Middleware.ContentType.Types as CT
 import           Network.Wai.Middleware.ContentType.Text
-import           Network.HTTP.Types                       (Status, ResponseHeaders)
+import           Network.HTTP.Types                       (status200, Status, ResponseHeaders)
 import           Network.Wai                              (Response)
 
 import           Clay.Render
@@ -14,9 +19,14 @@
 
 clay :: Monad m =>
         Config -> [App] -> Css
-     -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+     -> FileExtListenerT m ()
 clay c as i =
-  tell' $ HM.singleton CT.Css (clayOnly c as i)
+  tell' $ HM.singleton CT.Css $
+    ResponseVia
+      (c,as,i)
+      status200
+      [("Content-Type","text/css")]
+      (\(c,as,i) -> clayOnly c as i)
 
 {-# INLINEABLE clay #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Json.hs b/src/Network/Wai/Middleware/ContentType/Json.hs
--- a/src/Network/Wai/Middleware/ContentType/Json.hs
+++ b/src/Network/Wai/Middleware/ContentType/Json.hs
@@ -1,8 +1,12 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
 module Network.Wai.Middleware.ContentType.Json where
 
 import           Network.Wai.Middleware.ContentType.Types
 import           Network.Wai.Middleware.ContentType.ByteString
-import           Network.HTTP.Types                      (Status, ResponseHeaders)
+import           Network.HTTP.Types                      (status200, Status, ResponseHeaders)
 import           Network.Wai                             (Response)
 
 import qualified Data.Aeson                              as A
@@ -14,9 +18,10 @@
 json :: ( A.ToJSON j
         , Monad m
         ) => j
-          -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+          -> FileExtListenerT m ()
 json =
-  bytestring Json . A.encode
+  (overFileExts [Json] $ mapHeaders (("Content-Type","application/json"):))
+  . bytestring Json . A.encode
 
 {-# INLINEABLE json #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Julius.hs b/src/Network/Wai/Middleware/ContentType/Julius.hs
--- a/src/Network/Wai/Middleware/ContentType/Julius.hs
+++ b/src/Network/Wai/Middleware/ContentType/Julius.hs
@@ -1,8 +1,13 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
+
 module Network.Wai.Middleware.ContentType.Julius where
 
 import           Network.Wai.Middleware.ContentType.Types as CT
 import           Network.Wai.Middleware.ContentType.Text
-import           Network.HTTP.Types                       (Status, ResponseHeaders)
+import           Network.HTTP.Types                       (status200, Status, ResponseHeaders)
 import           Network.Wai                              (Response)
 
 import           Text.Julius
@@ -13,9 +18,14 @@
 
 julius :: Monad m =>
           Javascript
-       -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+       -> FileExtListenerT m ()
 julius i =
-  tell' $ HM.singleton CT.JavaScript (juliusOnly i)
+  tell' $ HM.singleton CT.JavaScript $
+    ResponseVia
+      i
+      status200
+      [("Content-Type","application/javascript")]
+      juliusOnly
 
 {-# INLINEABLE julius #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Lucid.hs b/src/Network/Wai/Middleware/ContentType/Lucid.hs
--- a/src/Network/Wai/Middleware/ContentType/Lucid.hs
+++ b/src/Network/Wai/Middleware/ContentType/Lucid.hs
@@ -1,7 +1,11 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
 module Network.Wai.Middleware.ContentType.Lucid where
 
 import           Network.Wai.Middleware.ContentType.Types
-import           Network.HTTP.Types                      (Status, ResponseHeaders)
+import           Network.HTTP.Types                      (status200, Status, ResponseHeaders)
 import           Network.Wai                             (Response, responseBuilder)
 
 import qualified Lucid.Base                              as L
@@ -13,10 +17,15 @@
 
 lucid :: Monad m =>
          L.HtmlT m ()
-      -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+      -> FileExtListenerT m ()
 lucid i = do
-  i' <- lift (lucidOnly i)
-  tell' (HM.singleton Html i')
+  f <- lift (lucidOnly i)
+  tell' $ HM.singleton Html $
+    ResponseVia
+      i
+      status200
+      [("Content-Type","text/html")]
+      (const f)
 
 {-# INLINEABLE lucid #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Lucius.hs b/src/Network/Wai/Middleware/ContentType/Lucius.hs
--- a/src/Network/Wai/Middleware/ContentType/Lucius.hs
+++ b/src/Network/Wai/Middleware/ContentType/Lucius.hs
@@ -1,8 +1,13 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
+
 module Network.Wai.Middleware.ContentType.Lucius where
 
 import           Network.Wai.Middleware.ContentType.Types as CT
 import           Network.Wai.Middleware.ContentType.Text
-import           Network.HTTP.Types                       (Status, ResponseHeaders)
+import           Network.HTTP.Types                       (status200, Status, ResponseHeaders)
 import           Network.Wai                              (Response)
 
 import           Text.Lucius
@@ -13,9 +18,14 @@
 
 lucius :: Monad m =>
           Css
-       -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+       -> FileExtListenerT m ()
 lucius i =
-  tell' $ HM.singleton CT.Css (luciusOnly i)
+  tell' $ HM.singleton CT.Css $
+    ResponseVia
+      i
+      status200
+      [("Content-Type","text/css")]
+      luciusOnly
 
 {-# INLINEABLE lucius #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Pandoc.hs b/src/Network/Wai/Middleware/ContentType/Pandoc.hs
--- a/src/Network/Wai/Middleware/ContentType/Pandoc.hs
+++ b/src/Network/Wai/Middleware/ContentType/Pandoc.hs
@@ -1,8 +1,13 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
+
 module Network.Wai.Middleware.ContentType.Pandoc where
 
 import           Network.Wai.Middleware.ContentType.Types
 import           Network.Wai.Middleware.ContentType.Text
-import           Network.HTTP.Types                       (Status, ResponseHeaders)
+import           Network.HTTP.Types                       (status200, Status, ResponseHeaders)
 import           Network.Wai                              (Response)
 
 import qualified Data.Text.Lazy                           as LT
@@ -14,9 +19,14 @@
 
 markdown :: Monad m =>
             P.Pandoc
-         -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+         -> FileExtListenerT m ()
 markdown i =
-  tell' $ HM.singleton Markdown (markdownOnly i)
+  tell' $ HM.singleton Markdown $
+    ResponseVia
+      i
+      status200
+      [("Content-Type","text/markdown")]
+      markdownOnly
 
 {-# INLINEABLE markdown #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Text.hs b/src/Network/Wai/Middleware/ContentType/Text.hs
--- a/src/Network/Wai/Middleware/ContentType/Text.hs
+++ b/src/Network/Wai/Middleware/ContentType/Text.hs
@@ -1,7 +1,11 @@
+{-# LANGUAGE
+    OverloadedStrings
+  #-}
+
 module Network.Wai.Middleware.ContentType.Text where
 
 import           Network.Wai.Middleware.ContentType.Types
-import           Network.HTTP.Types                       (Status, ResponseHeaders)
+import           Network.HTTP.Types                       (status200, Status, ResponseHeaders)
 import           Network.Wai                              (Response, responseBuilder)
 
 import qualified Data.Text.Lazy                           as LT
@@ -13,9 +17,14 @@
 
 text :: Monad m =>
         LT.Text
-     -> FileExtListenerT (Status -> ResponseHeaders -> Response) m ()
+     -> FileExtListenerT m ()
 text i =
-  tell' $ HM.singleton Text (textOnly i)
+  tell' $ HM.singleton Text $
+    ResponseVia
+      i
+      status200
+      [("Content-Type", "text/plain")]
+      textOnly
 
 {-# INLINEABLE text #-}
 
diff --git a/src/Network/Wai/Middleware/ContentType/Types.hs b/src/Network/Wai/Middleware/ContentType/Types.hs
--- a/src/Network/Wai/Middleware/ContentType/Types.hs
+++ b/src/Network/Wai/Middleware/ContentType/Types.hs
@@ -8,6 +8,7 @@
   , StandaloneDeriving
   , UndecidableInstances
   , MultiParamTypeClasses
+  , ExistentialQuantification
   , GeneralizedNewtypeDeriving
   #-}
 
@@ -27,10 +28,15 @@
   , allFileExts
   , getFileExt
   , toExt
+  , ResponseVia (..)
+  , runResponseVia
+  , mapStatus
+  , mapHeaders
   , FileExtMap
   , FileExtListenerT (..)
   , execFileExtListenerT
-  , mapResponse
+  , overFileExts
+  , mapFileExtMap
   , -- * Utilities
     tell'
   , AcceptHeader
@@ -118,9 +124,37 @@
 {-# INLINEABLE toExt #-}
 
 
+-- ayy, lamo. Basically.
+data ResponseVia = forall a. ResponseVia
+  { responseData     :: !a
+  , responseStatus   :: !Status
+  , responseHeaders  :: !ResponseHeaders
+  , responseFunction :: !(a -> Status -> ResponseHeaders -> Response)
+  }
 
-type FileExtMap a = HashMap FileExt a
+runResponseVia :: ResponseVia -> Response
+runResponseVia (ResponseVia d s hs f) = f d s hs
 
+mapStatus :: (Status -> Status) -> ResponseVia -> ResponseVia
+mapStatus f (ResponseVia d s hs f') = ResponseVia d (f s) hs f'
+
+mapHeaders :: (ResponseHeaders -> ResponseHeaders) -> ResponseVia -> ResponseVia
+mapHeaders f (ResponseVia d s hs f') = ResponseVia d s (f hs) f'
+
+overFileExts :: Monad m =>
+                [FileExt]
+             -> (ResponseVia -> ResponseVia)
+             -> FileExtListenerT m a
+             -> FileExtListenerT m a
+overFileExts fs f (FileExtListenerT xs) = do
+  i <- get
+  let i' = HM.mapWithKey (\k x -> if k `elem` fs then f x else x) i
+  (x, o) <- lift (runStateT xs i')
+  put o
+  pure x
+
+type FileExtMap = HashMap FileExt ResponseVia
+
 -- | The monad for our DSL - when using the combinators, our result will be this
 --   type:
 --
@@ -128,43 +162,39 @@
 --   > myListener = do
 --   >   text "Text!"
 --   >   json ("Json!" :: T.Text)
-newtype FileExtListenerT r m a = FileExtListenerT
-  { runFileExtListenerT :: StateT (FileExtMap r) m a
+newtype FileExtListenerT m a = FileExtListenerT
+  { runFileExtListenerT :: StateT FileExtMap m a
   } deriving ( Functor, Applicative, Alternative, Monad, MonadFix, MonadPlus, MonadIO
-             , MonadTrans, MonadReader r', MonadWriter w, MonadState (FileExtMap r)
+             , MonadTrans, MonadReader r', MonadWriter w, MonadState FileExtMap
              , MonadCont, MonadError e, MonadBase b, MonadThrow, MonadCatch
              , MonadMask, MonadLogger, MonadUrl b f, MFunctor
              )
 
-deriving instance (MonadResource m, MonadBase IO m) => MonadResource (FileExtListenerT r m)
+deriving instance (MonadResource m, MonadBase IO m) => MonadResource (FileExtListenerT m)
 
-instance MonadTransControl (FileExtListenerT r) where
-  type StT (FileExtListenerT r) a = StT (StateT (FileExtMap r)) a
+instance MonadTransControl FileExtListenerT where
+  type StT FileExtListenerT a = StT (StateT FileExtMap) a
   liftWith = defaultLiftWith FileExtListenerT runFileExtListenerT
   restoreT = defaultRestoreT FileExtListenerT
 
 instance ( MonadBaseControl b m
-         ) => MonadBaseControl b (FileExtListenerT r m) where
-  type StM (FileExtListenerT r m) a = ComposeSt (FileExtListenerT r) m a
+         ) => MonadBaseControl b (FileExtListenerT m) where
+  type StM (FileExtListenerT m) a = ComposeSt FileExtListenerT m a
   liftBaseWith = defaultLiftBaseWith
   restoreM     = defaultRestoreM
 
-mapResponse :: Monad m =>
-               ((Status -> ResponseHeaders -> Response) -> Response)
-            -> FileExtListenerT (Status -> ResponseHeaders -> Response) m a
-            -> FileExtListenerT Response m a
-mapResponse f (FileExtListenerT xs) =
-  FileExtListenerT $ mapState (HM.map f) (HM.map (const . const)) xs
-  where
-    mapState to from xs = do
-      i <- get
-      (x,s) <- lift (runStateT xs (from i))
-      put (to s)
-      pure x
-
-execFileExtListenerT :: Monad m => FileExtListenerT r m a -> m (FileExtMap r)
+execFileExtListenerT :: Monad m => FileExtListenerT m a -> m FileExtMap
 execFileExtListenerT xs = execStateT (runFileExtListenerT xs) mempty
 
+mapFileExtMap :: ( Monad m
+                 ) => (FileExtMap -> FileExtMap)
+                   -> FileExtListenerT m a
+                   -> FileExtListenerT m a
+mapFileExtMap f (FileExtListenerT xs) = do
+  map      <- get
+  (x,map') <- lift (runStateT xs (f map))
+  put map'
+  return x
 
 
 -- * Headers
@@ -205,7 +235,7 @@
 --   > myApp = do
 --   >   text "foo"
 --   >   invalidEncoding myErrorHandler -- handles all except text/plain
-invalidEncoding :: Monad m => r -> FileExtListenerT r m ()
+invalidEncoding :: Monad m => ResponseVia -> FileExtListenerT m ()
 invalidEncoding r = mapM_ (\t -> tell' $ HM.singleton t r) allFileExts
 
 {-# INLINEABLE invalidEncoding #-}
diff --git a/test/Network/Wai/Middleware/ContentTypeSpec.hs b/test/Network/Wai/Middleware/ContentTypeSpec.hs
--- a/test/Network/Wai/Middleware/ContentTypeSpec.hs
+++ b/test/Network/Wai/Middleware/ContentTypeSpec.hs
@@ -162,8 +162,8 @@
   fileExtsToMiddleware allExamples $
   (\req respond -> respond (textOnly "Something went wrong" status406 []))
 
-allExamples :: FileExtListenerT Response IO ()
-allExamples = mapResponse (\f -> f status200 []) $ do
+allExamples :: FileExtListenerT IO ()
+allExamples = do
   text "Text!"
   json ("Json!" :: T.Text)
   lucid (L.toHtmlRaw ("Html!" :: T.Text))
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
@@ -1,19 +1,14 @@
 Name:                   wai-middleware-content-type
-Version:                0.3.0
+Version:                0.4.0
 Author:                 Athan Clark <athan.clark@gmail.com>
 Maintainer:             Athan Clark <athan.clark@gmail.com>
 License:                BSD3
 License-File:           LICENSE
-Synopsis:               Route to different middlewares based on the incoming Accept header.
+Synopsis:               A simple WAI library for responding with content.
 -- Description:
 Cabal-Version:          >= 1.10
 Build-Type:             Simple
 Category:               Web
-
-
-Flag Example
-  Description:          Build a trivial example
-  Default:              False
 
 
 Library