diff --git a/binary-strict.cabal b/binary-strict.cabal
--- a/binary-strict.cabal
+++ b/binary-strict.cabal
@@ -1,5 +1,5 @@
 name:            binary-strict
-version:         0.4.7
+version:         0.4.7.1
 license:         BSD3
 license-file:    LICENSE
 author:          Lennart Kolmodin <kolmodin@dtek.chalmers.se>
@@ -31,3 +31,4 @@
 extra-source-files: tests/BitGetTest.hs, src/Data/Binary/Strict/Common.h
 ghc-options:     -Wall -fno-warn-name-shadowing
 build-type:      Simple
+build-depends:   mtl >= 2.1 && <2.2
diff --git a/src/Data/Binary/BitBuilder.hs b/src/Data/Binary/BitBuilder.hs
--- a/src/Data/Binary/BitBuilder.hs
+++ b/src/Data/Binary/BitBuilder.hs
@@ -37,9 +37,9 @@
 
 import Foreign
 import Data.Monoid
-import Data.Word
 import qualified Data.ByteString      as S
 import qualified Data.ByteString.Lazy as L
+import System.IO.Unsafe (unsafePerformIO)
 
 #ifdef BYTESTRING_IN_BASE
 import Data.ByteString.Base (inlinePerformIO)