--- old/src/hotspot/share/prims/jvm.cpp	2018-05-07 15:52:09.016464600 +0200
+++ new/src/hotspot/share/prims/jvm.cpp	2018-05-07 15:52:08.724459650 +0200
@@ -653,6 +653,7 @@
     ResourceMark rm(THREAD);
     THROW_MSG_0(vmSymbols::java_lang_CloneNotSupportedException(), klass->external_name());
   }
+  assert(!obj->klass_is_value_type(), "Disallowed on value type");
 
   // Make shallow object copy
   const int size = obj->size();