diff --git a/crypto/skcipher.c b/crypto/skcipher.c
index 46bb300d418fe7635416f223a020b652270d9094..b664cf867f5fb2cb358234f139b16b90795c5f64 100644
--- a/crypto/skcipher.c
+++ b/crypto/skcipher.c
@@ -131,8 +131,13 @@ int skcipher_walk_done(struct skcipher_walk *walk, int err)
 		memcpy(walk->dst.virt.addr, walk->page, n);
 		skcipher_unmap_dst(walk);
 	} else if (unlikely(walk->flags & SKCIPHER_WALK_SLOW)) {
-		if (WARN_ON(err)) {
-			/* unexpected case; didn't process all bytes */
+		if (err) {
+			/*
+			 * Didn't process all bytes.  Either the algorithm is
+			 * broken, or this was the last step and it turned out
+			 * the message wasn't evenly divisible into blocks but
+			 * the algorithm requires it.
+			 */
 			err = -EINVAL;
 			goto finish;
 		}