I've solved this problem. It was related to bug EJB-225. In the example above, the primary key class had a a reference to Card which was being loaded eagerly. I'm pretty sure the EJB3 spec says that the default should be lazy. Adding fetch=FetchType.LAZY to the mapping to Card in the primary key class also solved the problem described above. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3974094#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...