diff --git a/drivers/md/md.c b/drivers/md/md.c
index 11457a28a14cfa5967c7c69b62fb5479095dfdf1..61767f1962ebf39f5c96d72803147dd96b0c8bf5 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1652,6 +1652,8 @@ static void md_update_sb(mddev_t * mddev, int force_change)
 	int sync_req;
 	int nospares = 0;
 
+	if (mddev->external)
+		return;
 repeat:
 	spin_lock_irq(&mddev->write_lock);