diff --git a/Crypto/Threefish/Authenticated.hs b/Crypto/Threefish/Authenticated.hs
--- a/Crypto/Threefish/Authenticated.hs
+++ b/Crypto/Threefish/Authenticated.hs
@@ -22,10 +22,19 @@
 prng :: IORef SkeinGen
 prng = unsafePerformIO $ newSkeinGen >>= newIORef
 
+-- | Strict version of 'atomicModifyIORef'.  This forces both the value stored
+-- in the 'IORef' as well as the value returned.
+atomicModIORef' :: IORef a -> (a -> (a,b)) -> IO b
+atomicModIORef' ref f = do
+    b <- atomicModifyIORef ref
+            (\x -> let (a, b) = f x
+                    in (a, a `seq` b))
+    b `seq` return b
+
 -- | Generate a 256 bit nonce using the Skein PRNG.
 generateNonce :: IO Nonce256
 generateNonce =
-    Block256 `fmap` atomicModifyIORef' prng (pflip . randomBytes 32)
+    Block256 `fmap` atomicModIORef' prng (pflip . randomBytes 32)
   where
     pflip (a, b) = (b, a)
 
diff --git a/Crypto/Threefish/Skein.hs b/Crypto/Threefish/Skein.hs
--- a/Crypto/Threefish/Skein.hs
+++ b/Crypto/Threefish/Skein.hs
@@ -58,7 +58,7 @@
               BS.packCStringLen (castPtr ptr, outlen)
           | otherwise -> do
               let !chunk' =
-                    BSL.toStrict chunk
+                    toStrict chunk
                   (!lst, !len) =
                     if BSL.null rest
                       then (2, fromIntegral $ BS.length chunk')
@@ -67,6 +67,9 @@
                 skein256_update ctx (first .|. lst) msgtype len (castPtr ptr)
               go 0 rest ctx
 
+toStrict :: BSL.ByteString -> BS.ByteString
+toStrict = BS.concat . BSL.toChunks
+
 hash256 :: Word64 -> Key256 -> BSL.ByteString -> BS.ByteString
 hash256 outlen k bs =
     case init256 k outlen of
@@ -75,7 +78,7 @@
 {-# INLINE skein256 #-}
 -- | Hash a message using 256 bit Skein.
 skein256 :: BSL.ByteString -> Block256
-skein256 = Block256 . hash256 32 (Block256 "")
+skein256 = Block256 . hash256 32 (Block256 BS.empty)
 
 {-# INLINE skeinMAC256 #-}
 -- | Create a 256 bit Skein-MAC.
diff --git a/threefish.cabal b/threefish.cabal
--- a/threefish.cabal
+++ b/threefish.cabal
@@ -1,5 +1,5 @@
 name:                threefish
-version:             0.2.5
+version:             0.2.6
 synopsis:            The Threefish block cipher and the Skein hash function for Haskell.
 description:         Implements 256 and 512 bit variants of Threefish and Skein. Skein is usable as a "normal" hash function as well as in Skein-MAC, as a cryptographically secure PRNG, as a stream cipher and as a key derivation function, all implemented according to the specifications of the Skein 1.3 paper.
 homepage:            http://github.com/valderman/threefish
@@ -37,15 +37,15 @@
     MultiParamTypeClasses,
     FunctionalDependencies
   build-depends:
-    base >=4.6 && <5,
-    bytestring >=0.10,
-    cereal >=0.3,
-    array >=0.4,
-    crypto-api >=0.12,
-    tagged >=0.4,
-    data-default >=0.5,
+    base >=4.5 && <5,
+    bytestring >=0.10.4.0,
+    cereal >=0.4.0.1,
+    array >=0.4.0.0,
+    crypto-api >=0.12.2.2,
+    tagged >=0.7,
+    data-default >=0.5.3,
     random,
-    entropy >= 0.2.2.2
+    entropy
   default-language:    Haskell2010
   ghc-options: -Wall -O2
   include-dirs: cbits