Font change only affects top item in ComboBox

When I add multiple items to a comboBox, and I attempt to change the font, the font changes are *only* applied to the top item in the comboBox, even though all the items are displayed.

I often try to change the font size of all the font in the comboBox, for instance, when I want to make it smaller so that the whole widgit will fit somewhere on my mockup.

I'm on Mockups for Desktop v. 1.6.25