You must have a DiscriminatorValue defined. See EJB 3.0 Java Persistence API Final Release 2.1.9.1. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4000391#4000391 Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&p=4000391