Automatic navigation does not work with Inherited InputField

I have inherited the InputField class because I needed some additional features. Everything works fine, I can treat the object as a usual selectable (as I would normally expect). But automatic navigation between selectables seems to ignore objects of that class. Can I do something to cope with this?

The strange thing is that my InputField can be set as target as target in the Explicit navigation option.
But I really need the automatic navigation.