[NTG-context] How to box \useMPgraphic?

Hello all, I'd like to insert a little MetaPost square into the running text and properly align it vertically. So I tried: --- \startuseMPgraphic{square} draw unitsquare scaled StrutHeight; \stopuseMPgraphic \starttext I want a square \raisebox{-\strutdepth}{\useMPgraphic{square}} in my running text. \stoptext --- Unfortunately, to no avail. TeX seems to be asking for some boxed content, so I tried to wrap the figure inclusion into a box: \hbox{\useMPgraphic{square}}. It doesn't solve the problem either. What do I need to change? Oliver