Default Value: <none> not working for select list

I create a view reference field with select list widget, selected two views as "Views that can be referenced", and set the Default Value to .

When I create new content, the first of the two selectable views is selected in the select list, and only those two items are available in the list (i.e. no option "select a value").

I have set the field as required, but I'd still expect the select list to render with "select a value" or similar as default.