diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index db7ec14..dfc4e0d 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -768,8 +768,8 @@
 		return -EINVAL;
 	
 	rom = pci_map_rom(pdev, &size);	/* size starts out as PCI window size */
-	if (!rom)
-		return 0;
+	if (!rom || !size)
+		return -EIO;
 		
 	if (off >= size)
 		count = 0;