diff --git a/sys/vm/vm_phys.h b/sys/vm/vm_phys.h
index 153ef94391ef..575b93cde1a6 100644
--- a/sys/vm/vm_phys.h
+++ b/sys/vm/vm_phys.h
@@ -61,7 +61,7 @@ struct vm_phys_seg {
 };
 
 extern struct mem_affinity *mem_affinity;
-int *mem_locality;
+extern int *mem_locality;
 extern int vm_ndomains;
 extern struct vm_phys_seg vm_phys_segs[];
 extern int vm_phys_nsegs;