diff --git a/hw/pci.c b/hw/pci.c
index a7ff5668a7..11d9b70eca 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -227,6 +227,7 @@ void pci_bus_new_inplace(PCIBus *bus, DeviceState *parent,
                          const char *name, int devfn_min)
 {
     qbus_create_inplace(&bus->qbus, &pci_bus_info, parent, name);
+    assert(PCI_FUNC(devfn_min) == 0);
     bus->devfn_min = devfn_min;
 
     /* host bridge */
@@ -608,7 +609,7 @@ static PCIDevice *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus,
 {
     if (devfn < 0) {
         for(devfn = bus->devfn_min ; devfn < ARRAY_SIZE(bus->devices);
-            devfn += 8) {
+            devfn += PCI_FUNC_MAX) {
             if (!bus->devices[devfn])
                 goto found;
         }
diff --git a/hw/pci.h b/hw/pci.h
index 3a15bd4010..68d5c4ee25 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -14,6 +14,7 @@
 #define PCI_DEVFN(slot, func)   ((((slot) & 0x1f) << 3) | ((func) & 0x07))
 #define PCI_SLOT(devfn)         (((devfn) >> 3) & 0x1f)
 #define PCI_FUNC(devfn)         ((devfn) & 0x07)
+#define PCI_FUNC_MAX            8
 
 /* Class, Vendor and Device IDs from Linux's pci_ids.h */
 #include "pci_ids.h"