diff --git a/automotive-cse.cabal b/automotive-cse.cabal
--- a/automotive-cse.cabal
+++ b/automotive-cse.cabal
@@ -1,6 +1,6 @@
 
 name:                automotive-cse
-version:             0.1.5.0
+version:             0.1.6.0
 synopsis:            Automotive CSE emulation
 description:         This package includes Cryptography Security Engine (CSE)
                      codec emulation for automotive things.
diff --git a/src/Codec/Automotive/CSE/Internal.hs b/src/Codec/Automotive/CSE/Internal.hs
--- a/src/Codec/Automotive/CSE/Internal.hs
+++ b/src/Codec/Automotive/CSE/Internal.hs
@@ -20,7 +20,7 @@
   DerivedCipher, derivedCipher,
 
   KeyAuthUse, Auth, NotAuth,
-  makeKeyAuthUse, unKeyAuthUse,
+  makeKeyAuthUse', makeKeyAuthUse, unKeyAuthUse,
 
   UpdateC, Enc, Mac,
 
@@ -93,10 +93,13 @@
   KeyAuthUse ShortByteString
   deriving Eq
 
+makeKeyAuthUse' :: MonadPlus m => ShortByteString -> m (KeyAuthUse k)
+makeKeyAuthUse' k = do
+  guard $ Short.length k == 16
+  return $ KeyAuthUse k
+
 makeKeyAuthUse :: MonadPlus m => ByteString -> m (KeyAuthUse k)
-makeKeyAuthUse k = do
-  guard $ BS.length k == 16
-  return . KeyAuthUse $ Short.toShort k
+makeKeyAuthUse = makeKeyAuthUse' . Short.toShort
 
 unKeyAuthUse :: KeyAuthUse k -> ByteString
 unKeyAuthUse (KeyAuthUse bs) = Short.fromShort bs