[NTG-context] textbackground for text of different size

Dear List, the red highlight block in the following example is not covering the two 40pt characters: \definetextbackground[important][frame=no,background=color,backgroundcolor=red] \starttext abc\important{123{\switchtobodyfont[40pt]45}xy}z \stoptext Is there an option that fixes this? Thanks! Best, Sylvain