Trying to mark a conversation as long-running causes an exception (java.lang.NoClassDefFoundError: javassist/util/proxy/ProxyObject) when the ServletConversationManager tries to get a proxy for the httpSession.
The ProxyFactory.classLoaderProvider ends up resolving the classloader to an instance of org.apache.catalina.loader.StandardClassLoader (which doesn't know the javassist lib, since it's only in the app classloader).