--- old/src/hotspot/share/gc/z/zHeap.hpp	2017-12-21 17:35:43.641256828 +0900
+++ new/src/hotspot/share/gc/z/zHeap.hpp	2017-12-21 17:35:43.507254571 +0900
@@ -45,6 +45,8 @@
 #include "memory/allocation.hpp"
 
 class ZHeap VALUE_OBJ_CLASS_SPEC {
+  friend class VMStructs;
+
 private:
   static ZHeap*       _heap;