diff --git a/drivers/md/md.c b/drivers/md/md.c
index 4ebb5b4cbae1aa879e48d0d054bd6ddb68fa9b5a..b3bd35143c87ac46cd5f7d507060ea94a7c8c501 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -1096,6 +1096,7 @@ static int super_90_load(struct md_rdev *rdev, struct md_rdev *refdev, int minor
 	/* not spare disk, or LEVEL_MULTIPATH */
 	if (sb->level == LEVEL_MULTIPATH ||
 		(rdev->desc_nr >= 0 &&
+		 rdev->desc_nr < MD_SB_DISKS &&
 		 sb->disks[rdev->desc_nr].state &
 		 ((1<<MD_DISK_SYNC) | (1 << MD_DISK_ACTIVE))))
 		spare_disk = false;