Hi Thanks for spotting this, this is quite a nasty problem. You're correct in that it ought to be defensively copied while we still have locks on the node, to prevent this issue. I'm going to create a JIRA and unit test for this, but for the time being if you want a workaround you could try this: 1. Start a tx 2. Node.getData() 3. Make your own defensive copy. This won't be any more expensive than JBoss Cache doing this internally for you. 4. Commit your tx. That would guarantee that you don't end up with a ConcurrentModificationException. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4148077#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...