diff --git a/drivers/mtd/mtdraw.c b/drivers/mtd/mtdraw.c
index f63da7b..b716192 100644
--- a/drivers/mtd/mtdraw.c
+++ b/drivers/mtd/mtdraw.c
@@ -306,7 +306,7 @@
 	mtdraw->mtd = mtd;
 
 	mtdraw->cdev.ops = (struct cdev_operations *)&mtd_raw_fops;
-	mtdraw->cdev.size = mtd_div_by_wb(mtd->size, mtd) * mtdraw->rps;
+	mtdraw->cdev.size = (loff_t)mtd_div_by_wb(mtd->size, mtd) * mtdraw->rps;
 	mtdraw->cdev.name = basprintf("%s.raw", mtd->cdev.name);
 	mtdraw->cdev.priv = mtdraw;
 	mtdraw->cdev.dev = &mtd->class_dev;