[NTG-context] mathmatrix and grid

Dear list, I noticed that when using grid=both then the height of a mathmatrix is rounded down for no apparent reason whereas the depth is rounded up correctly. Visually it appears to me that the height should be rounded up here. In the MWE I added a \vrule to show that the determined height of the line definitely does not coincide with what one would expect. How can I fix that? MWE is below. Cheers, Henri --- \setuplayout[grid=both] \showgrid \starttext \input knuth \startformula \vrule % make lineheight and depth visible \startmathmatrix \NC A \NR \NC B \NR \NC C \NR \stopmathmatrix \stopformula \input tufte \stoptext