[NTG-context] Font for MetaPost graphics

The wiki claims setting up an MPenvironment is enough to change the font in MetaPost graphics: \startMPenvironment%[global] \switchtobodyfont [sans] \stopMPenvironment \starttext This should be serif. \startMPcode draw textext("This should be in sans."); \stopMPcode \stoptext However, this has no effect. All text is in default serif font. If [global] is provided, all text is in sans font. I am aware of a similar issue in a thread last year¹, but the solution didn't really address the problem. textext("\sans This should be sans.") works here, but the point is that the MPenvironment fails. Why is that? Marco [1] http://thread.gmane.org/gmane.comp.tex.context/69044