There was no serialVersionUid in the class, which is not a good idea I think... I added the serialVersionUid which was automatically generated in the old class (in jbpm 3.2), so jbpm 3.3 serialVersionUid should be compatible with jbpm 3.2 serialVersionUid... So in my eyes it is a correct solution (more correct would have been to add the versionUid at the beginning ;-)) View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4181167#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...