--- a/src/hotspot/share/prims/jvmtiExport.cpp	Wed Oct 17 18:31:48 2018 +0200
+++ b/src/hotspot/share/prims/jvmtiExport.cpp	Wed Oct 17 22:26:41 2018 +0200
@@ -1044,7 +1044,7 @@
  public:
    JvmtiObjectAllocEventMark(JavaThread *thread, oop obj) : JvmtiClassEventMark(thread, oop_to_klass(obj)) {
      _jobj = (jobject)to_jobject(obj);
-     _size = obj->size() * wordSize;
+     _size = Universe::heap()->obj_size(obj) * wordSize;
    };
    jobject jni_jobject() { return _jobj; }
    jlong size() { return _size; }