python add-in combobox to show self.value when first loaded

Using self.value it is possible to preset the value of the combo box (one of the values in the self.items list). But this value is not shown when the add-in is first loaded, you still see a blank combo box, even after self.refresh(). How can I show the selected value?

This is not the most important functionality, but I think it would make the add-in I'm working on more easily understood by users.