diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3cb961036637..0f7115b31ca3 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -5884,7 +5884,15 @@ consistency_policy_store(struct mddev *mddev, const char *buf, size_t len)
 		else
 			err = -EBUSY;
 	} else if (mddev->external && strncmp(buf, "ppl", 3) == 0) {
-		set_bit(MD_HAS_PPL, &mddev->flags);
+		/* md_run() holds the lock until ->pers is set */
+		err = mddev_lock(mddev);
+		if (err)
+			return err;
+		if (mddev->pers)
+			err = -EBUSY;
+		else
+			set_bit(MD_HAS_PPL, &mddev->flags);
+		mddev_unlock(mddev);
 	} else {
 		err = -EINVAL;
 	}