--- old/src/hotspot/share/gc/shared/genOopClosures.inline.hpp	2020-01-22 10:29:49.911807570 +0100
+++ new/src/hotspot/share/gc/shared/genOopClosures.inline.hpp	2020-01-22 10:29:49.439799846 +0100
@@ -118,6 +118,7 @@
   // Should we copy the obj?
   if (!CompressedOops::is_null(heap_oop)) {
     oop obj = CompressedOops::decode_not_null(heap_oop);
+    assert_object_is_in_heap(p, obj);
     if ((HeapWord*)obj < _boundary) {
       assert(!_g->to()->is_in_reserved(obj), "Scanning field twice?");
       oop new_obj = obj->is_forwarded() ? obj->forwardee()