[NTG-context] preventing page breaks after headings

Is there a way in MKII to ensure that there is never a page break between a heading and the following text? \setuphead[after={\page[no]}] does not seem to work without entering vertical mode before \page. But, so far, I have not found a way to enter vertical mode in after={…} that does not add interlinespace and thus place the text too far from the heading. Any suggestion or alternatives? Alan