diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c
index 423df92..7510cb3 100644
--- a/drivers/md/dm-thin.c
+++ b/drivers/md/dm-thin.c
@@ -1315,7 +1315,7 @@
 	if (bio_detain(pool->prison, &key, bio, &cell))
 		return;
 
-	if (bio_data_dir(bio) == WRITE)
+	if (bio_data_dir(bio) == WRITE && bio->bi_size)
 		break_sharing(tc, bio, block, &key, lookup_result, cell);
 	else {
 		struct dm_thin_endio_hook *h = dm_get_mapinfo(bio)->ptr;