That was an edge case discovered by one of our users: trying to close the session from within listener's onMessge() would lead to dead lock. Fixing required to be able to send acknowledgments before closing the session. Maintaining ackMode per acknowledgment instance is unnecessary. I was trying to cater for an use case that will actually never happen. Needs to be refactored at some point: http://jira.jboss.org/jira/browse/JBMESSAGING-642 View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=3986386#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...