diff --git a/include/kvm/pci.h b/include/kvm/pci.h
index 12bc01f..28d9ada 100644
--- a/include/kvm/pci.h
+++ b/include/kvm/pci.h
@@ -12,6 +12,7 @@
  */
 #define PCI_CONFIG_ADDRESS	0xcf8
 #define PCI_CONFIG_DATA		0xcfc
+#define PCI_CONFIG_BUS_FORWARD	0xcfa
 
 struct pci_config_address {
 	unsigned		zeros		: 2;		/* 1  .. 0  */