diff --git a/hw/pci.c b/hw/pci.c
index 44a1f9e526..df184f1829 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -558,7 +558,7 @@ PCIBus *pci_get_bus_devfn(int *devfnp, const char *devaddr)
         return NULL;
     }
 
-    *devfnp = slot << 3;
+    *devfnp = PCI_DEVFN(slot, 0);
     return pci_find_bus(pci_find_root_bus(dom), bus);
 }