diff --git a/drivers/pci/rom.c b/drivers/pci/rom.c
index c5d0a08a87473a24dc43dacb8081abf7c737b852..d6d499782fb43ad7083a7ce7f9627b75b2065407 100644
--- a/drivers/pci/rom.c
+++ b/drivers/pci/rom.c
@@ -69,6 +69,7 @@ size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
 {
 	void __iomem *image;
 	int last_image;
+	unsigned length;
 
 	image = rom;
 	do {
@@ -91,9 +92,9 @@ size_t pci_get_rom_size(struct pci_dev *pdev, void __iomem *rom, size_t size)
 		if (readb(pds + 3) != 'R')
 			break;
 		last_image = readb(pds + 21) & 0x80;
-		/* this length is reliable */
-		image += readw(pds + 16) * 512;
-	} while (!last_image);
+		length = readw(pds + 16);
+		image += length * 512;
+	} while (length && !last_image);
 
 	/* never return a size larger than the PCI resource window */
 	/* there are known ROMs that get the size wrong */