ComboBox Cue Banner not italic when DropDownStyle is DropDown

Question

We have a WinForms control that is an extended version of ComboBox that supports "cue banners" (aka watermarks) when there is no selection or text. Our control is similar to this implementation making use of CB_SETCUEBANNER.

However, when we set DropDownStyle for the control to ComboBoxStyle.DropDown (that is, also allows free text entry) the cue banner is showing, just not in italics (which is how it usually shows).

Does anyone know how to draw the cue banner in italics for a combo box in ComboBoxStyle.DropDown mode???