I've solved my problem which i belive is the same as yours. My solution was to use the em.merge instead of a em.persist. This is weird because my Owner object is new e.g. (has never been persist before). But this works!!!!! So basicly i have a check to see if child object has a known ID if so then merge else call persist. - Kevin View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3991427#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...