diff --git a/Language/Fay/Yesod.hs b/Language/Fay/Yesod.hs
--- a/Language/Fay/Yesod.hs
+++ b/Language/Fay/Yesod.hs
@@ -16,13 +16,30 @@
 -- | Call a command.
 call :: (Foreign a, Foreign command)
      => (Returns a -> command)
-     -> (a -> Fay ())
+     -> (a -> Fay ()) -- ^ Success Handler
      -> Fay ()
 call f g = ajaxCommand (f Returns) g
 
+-- ! Call a command, handling errors as well
+callWithErrorHandling :: (Foreign a, Foreign command)
+     => (Returns a -> command)
+     -> (a -> Fay ()) -- ^ Success Handler
+     -> (Fay ())      -- ^ Failure Handler
+     -> Fay ()
+callWithErrorHandling f g h = ajaxCommandWithErrorHandling (f Returns) g h
+
 -- | Run the AJAX command.
 ajaxCommand :: (Foreign a, Foreign command)
             => command
-            -> (a -> Fay ())
+            -> (a -> Fay ()) -- ^ Success Handler
             -> Fay ()
 ajaxCommand = ffi "jQuery['ajax']({ url: window['yesodFayCommandPath'], type: 'POST', data: { json: JSON.stringify(%1) }, dataType: 'json', success : %2})"
+
+-- | Run the AJAX command, handling errors as well
+ajaxCommandWithErrorHandling :: (Foreign a, Foreign command)
+            => command
+            -> (a -> Fay ()) -- ^ Success Handler
+            -> (Fay ())      -- ^ Failure Handler
+            -> Fay ()
+ajaxCommandWithErrorHandling = ffi "jQuery['ajax']({ url: window['yesodFayCommandPath'], type: 'POST', data: { json: JSON.stringify(%1) }, dataType: 'json', success : %2, error: %3})"
+
diff --git a/Yesod/Fay.hs b/Yesod/Fay.hs
--- a/Yesod/Fay.hs
+++ b/Yesod/Fay.hs
@@ -79,10 +79,10 @@
 import qualified Data.ByteString.Lazy       as L
 import           Data.Data                  (Data)
 import           Data.Default               (def)
-import           Data.Text                  (pack)
+import           Data.Text                  (pack, unpack)
 import           Data.Text.Encoding         (encodeUtf8)
 import           Data.Text.Lazy.Builder     (fromText, toLazyText)
-import           Filesystem                 (createTree)
+import           Filesystem                 (createTree, isFile, readTextFile)
 import           Filesystem.Path.CurrentOS  (directory, encodeString)
 #if MIN_VERSION_fay(0,10,0)
 import           Language.Fay               (compileFile)
@@ -206,13 +206,20 @@
         go Returns = jsonToRepJson . showToFay
 
 langYesodFay :: String
-langYesodFay = $(qRunIO $ fmap (LitE . StringL) $ readFile "Language/Fay/Yesod.hs")
+langYesodFay = $(qRunIO $ fmap (LitE . StringL . unpack) $ readTextFile "Language/Fay/Yesod.hs")
 
 writeYesodFay :: IO ()
 writeYesodFay = do
     let fp = "fay/Language/Fay/Yesod.hs"
-    createTree $ directory fp
-    writeFile (encodeString fp) langYesodFay
+        content = "-- NOTE: This file is auto-generated.\n" ++ langYesodFay
+    exists <- isFile fp
+    mcurrent <-
+        if exists
+            then fmap (Just . unpack) $ readTextFile fp
+            else return Nothing
+    unless (mcurrent == Just content) $ do
+        createTree $ directory fp
+        writeFile (encodeString fp) content
 
 requireJQuery :: YesodFay master => GWidget sub master ()
 requireJQuery = do
@@ -235,6 +242,7 @@
 fayFileProd :: FayFile
 fayFileProd name = do
     qAddDependentFile fp
+    qRunIO writeYesodFay
     eres <- qRunIO $ compileFile config fp
     case eres of
         Left e -> error $ "Unable to compile Fay module \"" ++ name ++ "\": " ++ show e
diff --git a/yesod-fay.cabal b/yesod-fay.cabal
--- a/yesod-fay.cabal
+++ b/yesod-fay.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                yesod-fay
-version:             0.1.0.4
+version:             0.1.1
 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
@@ -18,7 +18,7 @@
   exposed-modules:     Yesod.Fay
                        Language.Fay.Yesod
   build-depends:       base >= 4 && < 5
-                     , fay  >= 0.9
+                     , fay  >= 0.10
                      , transformers >= 0.2
                      , aeson >= 0.6
                      , bytestring >= 0.9