--- a/src/hotspot/share/gc/shenandoah/shenandoahBarrierSetClone.inline.hpp	Mon Sep 30 14:04:42 2019 +0200
+++ b/src/hotspot/share/gc/shenandoah/shenandoahBarrierSetClone.inline.hpp	Mon Sep 30 17:00:16 2019 +0200
@@ -73,7 +73,7 @@
 
 void ShenandoahBarrierSet::clone_barrier(oop obj) {
   assert(ShenandoahCloneBarrier, "only get here with clone barriers enabled");
-  if (!_heap->has_forwarded_objects()) return;
+  assert(_heap->has_forwarded_objects(), "only when heap is unstable");
 
   // This is called for cloning an object (see jvm.cpp) after the clone
   // has been made. We are not interested in any 'previous value' because