Apparently the class loader under which the object is deserialized is not the same loader under which the object was serialized. You mention you put the class in the lib directory of the server so that jBPM could get the value. How was it serialized in the first place? That is, where does the class definition you used to instantiate and set the value come from? If you placed your class in more than one location (e.g. the lib directory of your web module, the classes directory of your process archive) it will likely be loaded by different class loaders. View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4023507#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...