Because the rulebase does not get inserted into the (marshaller) context that's used for unmarshalling a WorkItem(Info),
when MarshallerReaderContext.resolveClass(ObjectStreamClass) get's called, it can not use the ruleBase's root class loader.

If necessary, I can supply a test case for this to show where it goes wrong – at the moment it disappeared with a stash I dropped so that I'll have to recreate it.