diff --git a/kernel/defs.h b/kernel/defs.h
index 049569e..62b9292 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -166,6 +166,7 @@ int             uvmcopy(pagetable_t, pagetable_t, uint64);
 void            uvmfree(pagetable_t, uint64);
 void            uvmunmap(pagetable_t, uint64, uint64, int);
 void            uvmclear(pagetable_t, uint64);
+pte_t *         walk(pagetable_t, uint64, int);
 uint64          walkaddr(pagetable_t, uint64);
 int             copyout(pagetable_t, uint64, char *, uint64);
 int             copyin(pagetable_t, char *, uint64, uint64);