--- old/src/hotspot/share/gc/g1/g1FullGCMarker.inline.hpp	2020-01-22 10:29:40.247649421 +0100
+++ new/src/hotspot/share/gc/g1/g1FullGCMarker.inline.hpp	2020-01-22 10:29:39.703640517 +0100
@@ -67,6 +67,8 @@
   T heap_oop = RawAccess<>::oop_load(p);
   if (!CompressedOops::is_null(heap_oop)) {
     oop obj = CompressedOops::decode_not_null(heap_oop);
+    assert_object_is_in_heap(p, obj);
+
     if (mark_object(obj)) {
       _oop_stack.push(obj);
       assert(_bitmap->is_marked(obj), "Must be marked now - map self");