diff --git a/arch/x86/include/asm/k8.h b/arch/x86/include/asm/k8.h
index f70e600..af00bd1 100644
--- a/arch/x86/include/asm/k8.h
+++ b/arch/x86/include/asm/k8.h
@@ -16,11 +16,16 @@
 extern int k8_scan_nodes(void);
 
 #ifdef CONFIG_K8_NB
+extern int num_k8_northbridges;
+
 static inline struct pci_dev *node_to_k8_nb_misc(int node)
 {
 	return (node < num_k8_northbridges) ? k8_northbridges[node] : NULL;
 }
+
 #else
+#define num_k8_northbridges 0
+
 static inline struct pci_dev *node_to_k8_nb_misc(int node)
 {
 	return NULL;