diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index e74143ccc36c1b669a08468ea10c54a562146de6..a26d82d945e1c70d379c7f16662ab3c1123e171a 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -249,6 +249,9 @@ static void pci_change_irq_level(PCIDevice *pci_dev, int irq_num, int change)
     PCIBus *bus;
     for (;;) {
         bus = pci_get_bus(pci_dev);
+        if (!bus) {
+            return;
+        }
         irq_num = bus->map_irq(pci_dev, irq_num);
         if (bus->set_irq)
             break;