diff --git a/Crypto/Cipher/DES/Primitive.hs b/Crypto/Cipher/DES/Primitive.hs
index 0abb35a..18a623c 100644
--- a/Crypto/Cipher/DES/Primitive.hs
+++ b/Crypto/Cipher/DES/Primitive.hs
@@ -29,7 +29,7 @@ type Bits56 = [Bool]
 type Bits64 = [Bool]
 
 desXor :: [Bool] -> [Bool] -> [Bool]
-desXor a b = zipWith xor a b
+desXor a b = zipWith (/=) a b
 
 desRotate :: [Bool] -> Int -> [Bool]
 desRotate bits rot = drop rot' bits ++ take rot' bits