diff --git a/tests/KAT_MiyaguchiPreneel.hs b/tests/KAT_MiyaguchiPreneel.hs
index 70fc389..8634b32 100644
--- a/tests/KAT_MiyaguchiPreneel.hs
+++ b/tests/KAT_MiyaguchiPreneel.hs
@@ -7,25 +7,22 @@ import           Crypto.ConstructHash.MiyaguchiPreneel
 import           Imports
 
 import           Data.Char (digitToInt)
-import qualified Data.ByteString as BS
+import qualified Data.ByteString.Char8 as B8
 import qualified Data.ByteArray as B
+import Data.ByteArray.Encoding (Base (Base16), convertFromBase)
 
 
 runMP128 :: ByteString -> ByteString
 runMP128 s = B.convert (mp s :: MiyaguchiPreneel AES128)
 
 hxs :: String -> ByteString
-hxs = BS.pack . rec' where
-    dtoW8 = fromIntegral . digitToInt
-    rec' (' ':xs)  =  rec' xs
-    rec' (x:y:xs)  =  dtoW8 x * 16 + dtoW8 y : rec' xs
-    rec' [_]       =  error "hxs: invalid hex pattern."
-    rec' []        =  []
+hxs = either (error . ("hxs:" ++)) id . convertFromBase Base16
+      . B8.pack . filter (/= ' ')
 
 gAES128 :: TestTree
 gAES128 =
   igroup "aes128"
-  [ runMP128  BS.empty
+  [ runMP128  B8.empty
     @?=       hxs "66e94bd4 ef8a2c3b 884cfa59 ca342b2e"
   , runMP128 (hxs "01000000 00000000 00000000 00000000")
     @?=       hxs "46711816 e91d6ff0 59bbbf2b f58e0fd3"