diff --git a/block/blk-settings.c b/block/blk-settings.c
index f1d4dfdc37a71..0fe16f987cdec 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -248,6 +248,13 @@ int blk_validate_limits(struct queue_limits *lim)
 	if (lim->io_min < lim->physical_block_size)
 		lim->io_min = lim->physical_block_size;
 
+	/*
+	 * The optimal I/O size may not be aligned to physical block size
+	 * (because it may be limited by dma engines which have no clue about
+	 * block size of the disks attached to them), so we round it down here.
+	 */
+	lim->io_opt = round_down(lim->io_opt, lim->physical_block_size);
+
 	/*
 	 * max_hw_sectors has a somewhat weird default for historical reason,
 	 * but driver really should set their own instead of relying on this