diff --git a/hw/ppc/ppc4xx_pci.c b/hw/ppc/ppc4xx_pci.c
index 3ea47df71f..cd3f192a13 100644
--- a/hw/ppc/ppc4xx_pci.c
+++ b/hw/ppc/ppc4xx_pci.c
@@ -320,7 +320,8 @@ static void ppc4xx_pcihost_realize(DeviceState *dev, Error **errp)
 
     b = pci_register_root_bus(dev, NULL, ppc4xx_pci_set_irq,
                               ppc4xx_pci_map_irq, s->irq, get_system_memory(),
-                              get_system_io(), 0, 4, TYPE_PCI_BUS);
+                              get_system_io(), 0, ARRAY_SIZE(s->irq),
+                              TYPE_PCI_BUS);
     h->bus = b;
 
     pci_create_simple(b, 0, "ppc4xx-host-bridge");