--- old/src/hotspot/share/oops/valueKlass.hpp	2018-05-07 15:52:08.388453956 +0200
+++ new/src/hotspot/share/oops/valueKlass.hpp	2018-05-07 15:52:08.076448668 +0200
@@ -49,7 +49,7 @@
     *((address*)adr_unpack_handler()) = NULL;
     assert(pack_handler() == NULL, "pack handler not null");
     *((int*)adr_default_value_offset()) = 0;
-
+    assert(Klass::ptr_is_value_type(this), "Value type klass ptr encoding");
   }
 
   ValueKlassFixedBlock* valueklass_static_bloc() const {