diff --git a/Web/ClientSession.hs b/Web/ClientSession.hs
--- a/Web/ClientSession.hs
+++ b/Web/ClientSession.hs
@@ -41,7 +41,6 @@
 import Foreign.Storable
 import System.IO.Unsafe
 import Language.Haskell.TH
-import qualified Data.Ascii as A
 
 type Key = S.ByteString
 
@@ -102,8 +101,8 @@
 
 encrypt :: S.ByteString -- ^ key
         -> S.ByteString -- ^ data
-        -> A.Ascii
-encrypt keyBS dataBS = A.unsafeFromByteString $ unsafePerformIO $
+        -> S.ByteString
+encrypt keyBS dataBS = unsafePerformIO $
     unsafeUseAsCString keyBS $ \keyPtr ->
         unsafeUseAsCStringLen dataBS $ \(dataPtr, dataLen) -> do
             let keyPtr' = castPtr keyPtr
@@ -117,9 +116,9 @@
                 unsafePackCStringFinalizer newPtr' len' $ free newPtr'
 
 decrypt :: S.ByteString -- ^ key
-        -> A.Ascii -- ^ data
+        -> S.ByteString -- ^ data
         -> Maybe S.ByteString
-decrypt keyBS dataA = unsafePerformIO $
+decrypt keyBS dataBS = unsafePerformIO $
     unsafeUseAsCString keyBS $ \keyPtr ->
         unsafeUseAsCStringLen dataBS $ \(dataPtr, dataLen) -> do
             let keyPtr' = castPtr keyPtr
@@ -136,8 +135,6 @@
                         bs <- unsafePackCStringFinalizer newPtr' len'
                             $ free newPtr'
                         return $ Just bs
-  where
-    dataBS = A.toByteString dataA
 
 foreign import ccall unsafe "encrypt"
     c_encrypt :: CUInt -> Ptr CUChar -> Ptr CUChar -> Ptr CUInt
diff --git a/clientsession.cabal b/clientsession.cabal
--- a/clientsession.cabal
+++ b/clientsession.cabal
@@ -1,5 +1,5 @@
 name:            clientsession
-version:         0.5.0
+version:         0.6.0
 license:         BSD3
 license-file:    LICENSE
 author:          Michael Snoyman <michael@snoyman.com>
@@ -22,7 +22,6 @@
                      bytestring >= 0.9 && < 0.10,
                      directory >= 1 && < 1.2,
                      random >= 1.0.0.2 && < 1.1,
-                     ascii >= 0.0.2 && < 0.1,
                      template-haskell
     exposed-modules: Web.ClientSession
     ghc-options:     -Wall