diff --git a/crypto/lrw.c b/crypto/lrw.c
index 6f9908a7ebcb..d38a382b09eb 100644
--- a/crypto/lrw.c
+++ b/crypto/lrw.c
@@ -132,7 +132,12 @@ static inline int get_index128(be128 *block)
 		return x + ffz(val);
 	}
 
-	return x;
+	/*
+	 * If we get here, then x == 128 and we are incrementing the counter
+	 * from all ones to all zeros. This means we must return index 127, i.e.
+	 * the one corresponding to key2*{ 1,...,1 }.
+	 */
+	return 127;
 }
 
 static int crypt(struct blkcipher_desc *d,