diff --git a/Yesod/Fay.hs b/Yesod/Fay.hs
--- a/Yesod/Fay.hs
+++ b/Yesod/Fay.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE FlexibleContexts      #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
@@ -105,13 +106,15 @@
 import           Language.Haskell.TH.Syntax (Exp (LitE), Lit (StringL),
                                              Q,
                                              qAddDependentFile, qRunIO)
-import           System.Environment         (getEnvironment)
+import           Control.Exception (IOException,catch)
+import           Prelude hiding (catch)
 import           System.Directory
+import           System.Environment         (getEnvironment)
 import           Text.Julius                (Javascript (Javascript), julius)
 import           Yesod.Core
+import           Yesod.Fay.Data
 import           Yesod.Form.Jquery          (YesodJquery (..))
 import           Yesod.Static
-import           Yesod.Fay.Data
 
 jsMainCall :: Bool -> String -> Builder
 jsMainCall False _ = mempty
@@ -207,7 +210,7 @@
                     Nothing -> error $ "Unable to parse input: " ++ show txt
                     Just cmd -> f go cmd
       where
-        go Returns = jsonToRepJson . showToFay
+        go Returns = returnJson . showToFay
 
 langYesodFay :: String
 langYesodFay = $(qRunIO $ fmap (LitE . StringL . unpack) $ readTextFile "Language/Fay/Yesod.hs")
@@ -265,11 +268,13 @@
       packageConf <- fmap (lookup "HASKELL_PACKAGE_SANDBOX") getEnvironment
       result <- compileFileWithState conf {
           configPackageConf = packageConf
+
         } fp
       case result of
         Left e -> return (Left e)
-        Right (source,state) -> do
+        Right (source',_,state) -> do
           let files = stateImported state
+              source = "\n(function(){\n" ++ source' ++ "\n})();\n"
               (fp_hi,fp_o) = refreshTo
           writeFile fp_hi (unlines (filter ours (map snd files)))
           writeFile fp_o source
@@ -300,7 +305,9 @@
              changed <- anyM (fmap (> thisModTime) . getModificationTime) modules
              if changed
                 then refresh
-                else fmap Right (readFile fp_o)
+                else catch (fmap Right (readFile fp_o))
+                           (\(_ :: IOException) ->
+                             refresh)
 
 -- | Does a full compile of the Fay code via GHC for type checking, and then
 -- embeds the Fay-generated Javascript as a static string. File changes during
@@ -360,6 +367,7 @@
         liftIO (compileFayFile (mkfp name) config
                 { configTypecheck = False
                 , configExportRuntime = exportRuntime
+                , configSourceMap = True
                 })
                 >>= \eres -> do
         (case eres of
diff --git a/yesod-fay.cabal b/yesod-fay.cabal
--- a/yesod-fay.cabal
+++ b/yesod-fay.cabal
@@ -2,10 +2,10 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                yesod-fay
-version:             0.4.0.3
+version:             0.4.0.4
 synopsis:            Utilities for using the Fay Haskell-to-JS compiler with Yesod.
 description:         For initial discussion, see <http://www.yesodweb.com/blog/2012/10/yesod-fay-js>. This is a work-in-progress.
-homepage:            https://github.com/snoyberg/yesod-fay
+homepage:            https://github.com/fpco/yesod-fay
 license:             MIT
 license-file:        LICENSE
 author:              Michael Snoyman