ComboBox with CustomValue enabled can not be cleared


when I call the clear()-Methode on an ComboBox and these ComboBox has the customValue allowed, it’s not possible to clear the ComboBox correct. The value will be cleared, but It will stay an value (it looks, like the index) in the field:

So I think the value is cleared, but the Text is not setted correct.

You can see the problem on the screenshot attached.

Can anyone help me? I’m using Vaadin 10.