diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
index ead008ea38f2..03fe2c5d5e32 100644
--- a/drivers/md/dm-writecache.c
+++ b/drivers/md/dm-writecache.c
@@ -1598,7 +1598,8 @@ static int writecache_map(struct dm_target *ti, struct bio *bio)
 
 	default:
 		BUG();
-		return -1;
+		wc_unlock(wc);
+		return DM_MAPIO_KILL;
 	}
 }