diff --git a/drivers/mtd/nand/nand_base.c b/drivers/mtd/nand/nand_base.c
index 30a3e9e742..d5c53fed1b 100644
--- a/drivers/mtd/nand/nand_base.c
+++ b/drivers/mtd/nand/nand_base.c
@@ -2628,7 +2628,7 @@ static struct nand_flash_dev *nand_get_flash_type(struct mtd_info *mtd,
 	chip->bbt_erase_shift = chip->phys_erase_shift =
 		ffs(mtd->erasesize) - 1;
 	if (chip->chipsize & 0xffffffff)
-		chip->chip_shift = ffs(chip->chipsize) - 1;
+		chip->chip_shift = ffs((unsigned)chip->chipsize) - 1;
 	else
 		chip->chip_shift = ffs((unsigned)(chip->chipsize >> 32)) + 31;