diff --git a/arch/arm/mach-footbridge/cats-pci.c b/arch/arm/mach-footbridge/cats-pci.c
index 35eb232..ae3e1c8 100644
--- a/arch/arm/mach-footbridge/cats-pci.c
+++ b/arch/arm/mach-footbridge/cats-pci.c
@@ -18,6 +18,9 @@
 
 static int __init cats_map_irq(struct pci_dev *dev, u8 slot, u8 pin)
 {
+	if (dev->irq >= 255)
+		return -1;	/* not a valid interrupt. */
+
 	if (dev->irq >= 128)
 		return dev->irq & 0x1f;