diff --git a/drivers/md/md.c b/drivers/md/md.c
index 32fc19c..1379b1a 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -8592,7 +8592,7 @@
 		goto err_mdp;
 	mdp_major = ret;
 
-	blk_register_region(MKDEV(MD_MAJOR, 0), 1UL<<MINORBITS, THIS_MODULE,
+	blk_register_region(MKDEV(MD_MAJOR, 0), 512, THIS_MODULE,
 			    md_probe, NULL, NULL);
 	blk_register_region(MKDEV(mdp_major, 0), 1UL<<MINORBITS, THIS_MODULE,
 			    md_probe, NULL, NULL);
@@ -8687,7 +8687,7 @@
 	struct list_head *tmp;
 	int delay = 1;
 
-	blk_unregister_region(MKDEV(MD_MAJOR,0), 1U << MINORBITS);
+	blk_unregister_region(MKDEV(MD_MAJOR,0), 512);
 	blk_unregister_region(MKDEV(mdp_major,0), 1U << MINORBITS);
 
 	unregister_blkdev(MD_MAJOR,"md");