diff --git a/drivers/mtd/parsers/redboot.c b/drivers/mtd/parsers/redboot.c
index 4f3bcc59a638..3351be651473 100644
--- a/drivers/mtd/parsers/redboot.c
+++ b/drivers/mtd/parsers/redboot.c
@@ -102,7 +102,7 @@ static int parse_redboot_partitions(struct mtd_info *master,
 			offset -= master->erasesize;
 		}
 	} else {
-		offset = directory * master->erasesize;
+		offset = (unsigned long) directory * master->erasesize;
 		while (mtd_block_isbad(master, offset)) {
 			offset += master->erasesize;
 			if (offset == master->size)