diff --git a/disk/part_dos.c b/disk/part_dos.c
index aae9d95906..8ddc13b50c 100644
--- a/disk/part_dos.c
+++ b/disk/part_dos.c
@@ -93,7 +93,8 @@ static int test_block_type(unsigned char *buffer)
 static int part_test_dos(struct blk_desc *dev_desc)
 {
 #ifndef CONFIG_SPL_BUILD
-	ALLOC_CACHE_ALIGN_BUFFER(legacy_mbr, mbr, 1);
+	ALLOC_CACHE_ALIGN_BUFFER(legacy_mbr, mbr,
+			DIV_ROUND_UP(dev_desc->blksz, sizeof(legacy_mbr)));
 
 	if (blk_dread(dev_desc, 0, 1, (ulong *)mbr) != 1)
 		return -1;