--- a/sysdep/unix/krt.h
+++ b/sysdep/unix/krt.h
@@ -112,7 +112,7 @@ struct kif_proto {
   struct kif_state sys;		/* Sysdep state */
 };
 
-struct kif_proto *kif_proto;
+extern struct kif_proto *kif_proto;
 
 #define KIF_CF ((struct kif_config *)p->p.cf)