diff -r 4cbfa5077d68 -r 623722a6aeb9 src/hotspot/share/gc/z/zOopClosures.inline.hpp
--- a/src/hotspot/share/gc/z/zOopClosures.inline.hpp	Mon Nov 25 12:32:40 2019 +0100
+++ b/src/hotspot/share/gc/z/zOopClosures.inline.hpp	Mon Nov 25 12:33:15 2019 +0100
@@ -96,7 +96,7 @@
     // oop here again (the object would be strongly live and we would
     // not consider clearing such oops), so therefore we don't have an
     // ABA problem here.
-    Atomic::cmpxchg(oop(NULL), p, obj);
+    Atomic::cmpxchg(p, obj, oop(NULL));
   }
 }