diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 88bf5a9ce573..67d56c92c8a4 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -8580,6 +8580,9 @@ static int check_reshape(struct mddev *mddev)
 	if (!check_stripe_cache(mddev))
 		return -ENOSPC;
 
+	if (mddev->bitmap_id == ID_LLBITMAP &&
+	    mddev->new_chunk_sectors < mddev->chunk_sectors)
+		return -EOPNOTSUPP;
 	if (mddev->new_chunk_sectors > mddev->chunk_sectors ||
 	    mddev->delta_disks > 0)
 		if (resize_chunks(conf,