Enums leak from properties to parent objects

An enum defined in class A and used as a property works fine inside a binding and a javascript function
Using the same enum from class A in a new class B also works fine inside a binding and a javascript function.
Deriving class C from class B and using the Q_OBJECT macro, Makes the enum work inside the binding, but using the same enum inside a javascript function doesn't.

Attached an example which instantiates all 3 classes and using a binding to set the enum.
3 Buttons are defined which use a Javascript function to update the enum properties. Using the "Change Object C" button, results in no change of the property but shows the following warning:

qrc:/main.qml:45: Error: Cannot assign [undefined] to int

None of this should actually work. We need to output a warning when we detect it and deprecate this behavior.