I answer to myself. Before to do the setXXX(), I must delete the previous object.
Like this : POJOUser user = pm.getObjectById(POJOUser.class, username); pm.deletePersistent(user.getLastLocation()); user.setLastLocation(new POJOLocation(newLocation)); And now, it works. Moreover, old references are deleted of the store. I hope this tips will help someone. Yoann -- You received this message because you are subscribed to the Google Groups "Google App Engine for Java" group. To post to this group, send email to google-appengine-j...@googlegroups.com. To unsubscribe from this group, send email to google-appengine-java+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine-java?hl=en.