I scheduled JBPM-2703 for release 4.4 and am following this discussion with interest. Maciej, did you write a test case of your own to check the patch? Huisheng, perhaps you did not apply the patch? jBPM 3.2 also had this problem and I resolved it in much the same way as Maciej does in his patch - by involving the context class loader in resolving classes. I'd be surprised if, after applying the patch, the problem persisted.