Caption and html in TwinColSelect

Can't see the setCaption String, or constructor caption parameter anywhere. Left and right caption works. Also setCaptionAsHtml doesn't seem to make captions rendered as html. Vaadin 8.0.1 (and Spring Boot).

@Override
protected void init(VaadinRequest request) {
   personSelect = new TwinColSelect<>("<h1>Select persons</h1>");
   personSelect.setCaptionAsHtml(true);
   personSelect.setRightColumnCaption("<h2>Selected Persons</h2>");
   personSelect.setLeftColumnCaption("<div style=\"color:green\">Available Persons</div>");
   personSelect.setDataProvider(DataProvider.fromStream(list1.stream()));
   personSelect.setItemCaptionGenerator(Person::getCaption);
   personSelect.select(list1.get(0), list1.get(5)); setContent(personSelect);
}

This renders the left and right column caption as plain text and the main caption is nowhere to be seen.

Also it seem the left column caption is left-aligned to the left side of the listbox, while the right side caption seems to have some left padding.

When placing the TwinColSelect inside a layout the main caption appears in html rendering. The right and left "sub"-captions aren't html-renderable, i guess.