diff --git a/yesod-static/Yesod/EmbeddedStatic.hs b/yesod-static/Yesod/EmbeddedStatic.hs
index 40345a10..e8196302 100644
--- a/yesod-static/Yesod/EmbeddedStatic.hs
+++ b/yesod-static/Yesod/EmbeddedStatic.hs
@@ -67,7 +67,7 @@ import Yesod.Core.Types
           )
 import qualified Data.ByteString.Lazy as BL
 import qualified Data.Text as T
-import qualified Data.Map as M
+import qualified Data.HashMap.Strict as M
 import qualified WaiAppStatic.Storage.Embedded as Static
 
 import Yesod.EmbeddedStatic.Types
diff --git a/yesod-static/Yesod/EmbeddedStatic/Internal.hs b/yesod-static/Yesod/EmbeddedStatic/Internal.hs
index 8f8ad8ff..0882c16d 100644
--- a/yesod-static/Yesod/EmbeddedStatic/Internal.hs
+++ b/yesod-static/Yesod/EmbeddedStatic/Internal.hs
@@ -3,6 +3,7 @@
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE TupleSections #-}
 {-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE CPP #-}
 module Yesod.EmbeddedStatic.Internal (
       EmbeddedStatic(..)
     , Route(..)
@@ -34,16 +35,26 @@ import Yesod.Core
 import qualified Data.ByteString.Lazy as BL
 import qualified Data.Text as T
 import qualified Data.Text.Encoding as T
-import qualified Data.Map as M
+import qualified Data.HashMap.Strict as M
 import qualified WaiAppStatic.Storage.Embedded as Static
 
 import Yesod.Static (base64md5)
 import Yesod.EmbeddedStatic.Types
 
+#if !MIN_VERSION_base(4,6,0)
+-- copied from base
+atomicModifyIORef' :: IORef a -> (a -> (a,b)) -> IO b
+atomicModifyIORef' ref f = do
+    b <- atomicModifyIORef ref
+            (\x -> let (a, b) = f x
+                    in (a, a `seq` b))
+    b `seq` return b
+#endif
+
 -- | The subsite for the embedded static file server.
 data EmbeddedStatic = EmbeddedStatic {
     stApp :: !Application
-  , widgetFiles :: !(IORef (M.Map T.Text File))
+  , widgetFiles :: !(IORef (M.HashMap T.Text File))
 }
 
 instance RenderRoute EmbeddedStatic where
diff --git a/yesod-static/test/EmbedProductionTest.hs b/yesod-static/test/EmbedProductionTest.hs
index 8fd407a3..d7fcbc1d 100644
--- a/yesod-static/test/EmbedProductionTest.hs
+++ b/yesod-static/test/EmbedProductionTest.hs
@@ -15,7 +15,8 @@ import Yesod.EmbeddedStatic
 import Yesod.Test
 import qualified Data.ByteString as B
 import qualified Data.ByteString.Lazy as BL
-import qualified Data.Text.Encoding as T
+import qualified Data.Text.Lazy as TL
+import qualified Data.Text.Lazy.Encoding as TL
 
 mkEmbeddedStatic False "eProduction" [testGen]
 
@@ -110,7 +111,7 @@ embedProductionSpecs = yesodSpec (MyApp eProduction) $ do
             [script] <- htmlQuery "script"
             let src = BL.takeWhile (/= 34) $ BL.drop 1 $ BL.dropWhile (/= 34) script -- 34 is "
 
-            get $ T.decodeUtf8 $ BL.toStrict src
+            get $ TL.toStrict $ TL.decodeUtf8 src
             statusIs 200
             hasCacheControl
             assertHeader "Content-Type" "application/javascript"
diff --git a/yesod-static/yesod-static.cabal b/yesod-static/yesod-static.cabal
index a5ccc0d7..9db09b9c 100644
--- a/yesod-static/yesod-static.cabal
+++ b/yesod-static/yesod-static.cabal
@@ -52,6 +52,7 @@ library
                    , process-conduit       >= 1.0      && < 1.1
                    , filepath              >= 1.3
                    , resourcet             >= 0.4
+                   , unordered-containers  >= 0.2
 
     exposed-modules: Yesod.Static
                      Yesod.EmbeddedStatic
@@ -101,6 +102,7 @@ test-suite tests
                    , process-conduit
                    , filepath
                    , resourcet
+                   , unordered-containers
 
     ghc-options:     -Wall