Hello, same problem here since 4.0.5.GA. We have configured @ActivationConfigProperty(propertyName="maxPoolSize", propertyValue="1") because we need a singleton MDB. What is the right way to solve such issues? There is no property 'maxPoolSize' in the class JmsActivationSpec in 4.0.5.GA and not either in 4.0.4.GA, where the MDB is working well. So, something has changed, but what? Klaus Erber View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3980733#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...