CascadingDropDown is there any way not to show PromptText

I'm using CascadingDropDown and I can't figure out how to get rid of first item (PromptText) in dropdown. I know that my second dropdown always contains at least one item, so I don't want to show PromtText at all and I want to select first item by default. I tried not to use PromptText in CascadingDropDown, but DropDown is always disabled in this case. Is there any way to do what I want?

See work item8672. It discusses not having to require PromptText.