diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 19598bd38939..6ba12f0f0f03 100644
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1496,7 +1496,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
 		if (!r1_bio->bios[i])
 			continue;
 
-		if (first_clone) {
+		if (first_clone && test_bit(WriteMostly, &rdev->flags)) {
 			/* do behind I/O ?
 			 * Not if there are too many, or cannot
 			 * allocate memory, or a reader on WriteMostly