diff --git a/Storage/Hashed/Monad.hs b/Storage/Hashed/Monad.hs
--- a/Storage/Hashed/Monad.hs
+++ b/Storage/Hashed/Monad.hs
@@ -188,7 +188,7 @@
         megs = (* (1024 * 1024))
         age (_, (_, a)) (_, (_, b)) = compare a b
 
-instance (Monad m, MonadError e m) => TreeRO (TreeMonad m) where
+instance (Functor m, Monad m, MonadError e m) => TreeRO (TreeMonad m) where
     expandTo p =
         do t <- gets tree
            p' <- (`catPaths` p) `fmap` ask
diff --git a/Storage/Hashed/Test.hs b/Storage/Hashed/Test.hs
--- a/Storage/Hashed/Test.hs
+++ b/Storage/Hashed/Test.hs
@@ -471,14 +471,6 @@
 instance Arbitrary BL.ByteString where
     arbitrary = BL.pack `fmap` arbitrary
 
-instance Arbitrary Word32 where
-    arbitrary = do x <- arbitrary :: Gen Int
-                   return $ fromIntegral x
-
-instance Arbitrary Word8 where
-    arbitrary = do x <- arbitrary :: Gen Int
-                   return $ fromIntegral x
-
 instance Arbitrary Hash where
     arbitrary = sized hash'
         where hash' 0 = return NoHash
@@ -487,16 +479,6 @@
                 case tag of
                   0 -> SHA256 . BS.pack <$> sequence [ arbitrary | _ <- [1..32] ]
                   1 -> SHA1 . BS.pack <$> sequence [ arbitrary | _ <- [1..20] ]
-
-instance Arbitrary Word64 where
-    arbitrary = do x <- arbitrary :: Gen Int
-                   y <- arbitrary :: Gen Int
-                   let x' = fromIntegral x
-                       y' = fromIntegral y
-                   return $ x' .|. (y' `shift` 32)
-
-instance Arbitrary Int64 where
-    arbitrary = fromIntegral `fmap` (arbitrary :: Gen Word64)
 
 instance (Monad m) => Arbitrary (TreeItem m) where
   arbitrary = sized tree'
diff --git a/hashed-storage.cabal b/hashed-storage.cabal
--- a/hashed-storage.cabal
+++ b/hashed-storage.cabal
@@ -1,5 +1,5 @@
 name:          hashed-storage
-version:       0.5.3
+version:       0.5.4
 synopsis:      Hashed file storage support code.
 
 description:   Support code for reading and manipulating hashed file storage
@@ -97,7 +97,7 @@
       build-depends: test-framework,
                      test-framework-hunit,
                      test-framework-quickcheck2,
-                     QuickCheck >= 2, HUnit, process >= 1.0.1, zip-archive
+                     QuickCheck >= 2.3, HUnit, process >= 1.0.1, zip-archive
     else
       buildable: False