diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 35b390a78..ee1c3f476 100755
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -2032,6 +2032,8 @@ static void __exit null_exit(void)
 
 	if (g_queue_mode == NULL_Q_MQ && shared_tags)
 		blk_mq_free_tag_set(&tag_set);
+
+	mutex_destroy(&lock);
 }
 
 module_init(null_init);