When you take a look at the source class at top of your stacktrace, you'll see that this exception occurs when the execution is null. Ie your process instance or subexecution does not exist (anymore). As Ronald states, without a complete unit test we can only guess about the cause. I see that Tom already added a more clear message in the trunk version. View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4251814#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...