diff --git a/drivers/md/md.c b/drivers/md/md.c
index f27e8f644dfe..8c1f7954882a 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2303,6 +2303,8 @@ static int add_new_disk(mddev_t * mddev, mdu_disk_info_t *info)
 		else
 			rdev->in_sync = 0;
 
+		rdev->sb_size = MD_SB_BYTES;
+
 		if (info->state & (1<<MD_DISK_WRITEMOSTLY))
 			set_bit(WriteMostly, &rdev->flags);