--- a/src/hotspot/share/gc/z/zRootsIterator.hpp	Wed Feb 20 13:43:01 2019 +0100
+++ b/src/hotspot/share/gc/z/zRootsIterator.hpp	Wed Feb 20 13:43:02 2019 +0100
@@ -31,9 +31,9 @@
 #include "runtime/thread.hpp"
 #include "utilities/globalDefinitions.hpp"
 
-class ZRootsIteratorClosure : public OopClosure, public ThreadClosure {
+class ZRootsIteratorClosure : public OopClosure {
 public:
-  virtual void do_thread(Thread* thread);
+  virtual void do_thread(Thread* thread) {}
 };
 
 typedef OopStorage::ParState<true /* concurrent */, false /* is_const */> ZOopStorageIterator;