diff --git a/src/Data/Unique/Really.hs b/src/Data/Unique/Really.hs
--- a/src/Data/Unique/Really.hs
+++ b/src/Data/Unique/Really.hs
@@ -11,7 +11,7 @@
 import Control.Applicative
 import System.IO.Unsafe (unsafePerformIO)
 
-#if __GLASGOW_HASKELL__
+#if UseGHC
 
 import Control.Exception (evaluate)
 import qualified Data.Unique
@@ -33,7 +33,7 @@
 
 hashUnique (Unique s) = hashStableName s
 
-instance Hashable Unique where hash = hashUnique
+instance Hashable Unique where hashWithSalt s = hashWithSalt s . hashUnique
 
 #else
 
diff --git a/src/Data/Vault/ST.hs b/src/Data/Vault/ST.hs
--- a/src/Data/Vault/ST.hs
+++ b/src/Data/Vault/ST.hs
@@ -28,7 +28,7 @@
     for the second implementation that doesn't need to
     bypass the type checker.
 -}
-#if __GLASGOW_HASKELL__
+#if UseGHC
 import qualified Data.Vault.ST_GHC as ST
 #else
 import qualified Data.Vault.ST_Pure as ST
diff --git a/src/Data/Vault/ST_GHC.hs b/src/Data/Vault/ST_GHC.hs
--- a/src/Data/Vault/ST_GHC.hs
+++ b/src/Data/Vault/ST_GHC.hs
@@ -9,6 +9,7 @@
 import qualified Data.IntMap as IntMap
 import Data.IORef
 import Control.Monad.ST
+import Control.Monad.ST.Unsafe
 
 
 import Data.Unique.Really
@@ -37,7 +38,7 @@
 empty = Vault Map.empty
 
 newKey :: ST s (Key s a)
-newKey = unsafeIOToST $ Key <$> newUnique
+newKey = Control.Monad.ST.Unsafe.unsafeIOToST $ Key <$> newUnique
 
 lookup :: Key s a -> Vault s -> Maybe a
 lookup (Key k) (Vault m) = fromAny <$> Map.lookup k m
diff --git a/src/Data/Vault/ST_Pure.hs b/src/Data/Vault/ST_Pure.hs
--- a/src/Data/Vault/ST_Pure.hs
+++ b/src/Data/Vault/ST_Pure.hs
@@ -10,6 +10,7 @@
 import Control.Monad.ST
 
 import System.IO.Unsafe (unsafePerformIO)
+import Control.Monad.ST.Unsafe
 
 import Data.Unique
 
@@ -41,7 +42,8 @@
 empty  = Vault Map.empty
 
 newKey :: ST s (Key s a)
-newKey = unsafeIOToST $ Key <$> newUnique <*> newIORef Nothing
+newKey = Control.Monad.ST.Unsafe.unsafeIOToST $
+    Key <$> newUnique <*> newIORef Nothing
 
 lookup :: Key s a -> Vault s -> Maybe a
 lookup key@(Key k _)   (Vault m) = unlock key =<< Map.lookup k m
diff --git a/vault.cabal b/vault.cabal
--- a/vault.cabal
+++ b/vault.cabal
@@ -1,5 +1,5 @@
 Name:               vault
-Version:            0.2.0.1
+Version:            0.2.0.3
 Synopsis:           a persistent store for values of arbitrary types
 Description:
   A /vault/ is a persistent store for values of arbitrary types.
@@ -28,19 +28,28 @@
     type:           git
     location:       git://github.com/HeinrichApfelmus/vault.git
 
+
+flag UseGHC
+    description: Use GHC-specific packages and extensions.
+    default:     True
+    
 Library
     hs-source-dirs:     src
     build-depends:      base == 4.*, containers >= 0.4 && < 0.6
-    if impl(ghc)
+    if impl(ghc) && flag(UseGHC)
         build-depends:  unordered-containers >= 0.2.1.0 && < 0.3,
-                        hashable == 1.1.*
+                        hashable >= 1.1 && < 1.3 
+        CPP-options:    -DUseGHC
 
-    ghc-options:        -Wall
     extensions:         CPP
+--    ghc-options:        -Wall
+
     exposed-modules:
                         Data.Vault,
                         Data.Vault.ST,
                         Data.Unique.Really
-    other-modules:
-                        Data.Vault.ST_GHC,
-                        Data.Vault.ST_Pure
+                        
+    if impl(ghc) && flag(UseGHC)
+        other-modules: Data.Vault.ST_GHC
+    else
+        other-modules: Data.Vault.ST_Pure