What causes "java.lang.IncompatibleClassChangeError: vtable stub"? In our application, we have seen this error pop up randomly and very seldom (just twice so far, and we run it a lot). It is not readily reproducible, even when restarting the app, using the same jvm/jars without rebuilding. As for our build process, we clean all classes/jars and rebuild them, so it's not the same problem as others have encountered where they made a change in one class and didn't recompile some other dependent classes. This is unlike some of the other questions related to IncompatibleClassChangeError -- none of them mention "vtable stub". In fact, there are surprisingly few google results when searching for "IncompatibleClassChangeError "vtable stub"".