diff --git a/drivers/mtd/maps/esb2rom.c b/drivers/mtd/maps/esb2rom.c
index a9d808a..d63c060 100644
--- a/drivers/mtd/maps/esb2rom.c
+++ b/drivers/mtd/maps/esb2rom.c
@@ -214,6 +214,9 @@ static int __devinit esb2rom_init_one(struct pci_dev *pdev,
 
 	/* reserved  0x0020 and 0x0010 */
 	window->phys -= 0x400000UL;
+#ifdef CONFIG_64BIT
+	window->phys &= 0xffffffffUL;
+#endif
 	window->size = (0xffffffffUL - window->phys) + 1UL;
 
 	/* Enable writes through the rom window */