diff --git a/drivers/md/md.c b/drivers/md/md.c
index 194580fba7fd..14d3b37944df 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -284,6 +284,8 @@ static blk_qc_t md_make_request(struct request_queue *q, struct bio *bio)
 	 * go away inside make_request
 	 */
 	sectors = bio_sectors(bio);
+	/* bio could be mergeable after passing to underlayer */
+	bio->bi_rw &= ~REQ_NOMERGE;
 	mddev->pers->make_request(mddev, bio);
 
 	cpu = part_stat_lock();