Long story short – MXBean is a runtime dependency. Some internal machinery for handling user defined MXBeans is missing in Java 5. For details please refer to http://java.sun.com/javase/6/docs/technotes/guides/jmx/enhancements.html. The second bullet on the top says:
MXBeans have been added. MXBeans are MBeans that provide a convenient way to bundle related values together without requiring clients to be specially configured to handle the bundles. A defined set of MXBeans already existed in the J2SE 5.0 platform, but Java SE 6 introduces an API to allow you to program your own custom MXBeans.
Although there is absolutely nothing wrong with your patch, would you be terribly disappointed if I leave the things the way they are and simply close this jira as "won't fix"?