--- old/src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.cpp	2019-12-11 23:05:19.893009903 +0100
+++ new/src/hotspot/share/gc/shenandoah/shenandoahBarrierSet.cpp	2019-12-11 23:05:19.785009899 +0100
@@ -265,7 +265,12 @@
 
   ShenandoahMarkingContext* const marking_context = _heap->marking_context();
   if (_heap->is_concurrent_root_in_progress() && !marking_context->is_marked(obj)) {
-    return NULL;
+    Thread* thr = Thread::current();
+    if (thr->is_Java_thread()) {
+      return NULL;
+    } else {
+      return obj;
+    }
   }
 
   oop fwd = load_reference_barrier_not_null(obj);