--- old/src/hotspot/share/gc/z/zCollectedHeap.hpp	2017-12-21 17:35:43.346251859 +0900
+++ new/src/hotspot/share/gc/z/zCollectedHeap.hpp	2017-12-21 17:35:43.211249584 +0900
@@ -33,6 +33,8 @@
 #include "gc/z/zStat.hpp"
 
 class ZCollectedHeap : public CollectedHeap {
+  friend class VMStructs;
+
 private:
   ZCollectorPolicy* _policy;
   ZBarrierSet       _barrier;