[NTG-context] vertical align in combination

Dear list, I have the following sample: \starttext \setupexternalfigure[location=default] \startcombination[nx=3, ny=2, location={middle}] {\externalfigure[mill.png][width=.25\textwidth]} {\externalfigure[cow.pdf][width=.25\textwidth]} {\externalfigure[cow.pdf][width=.25\textwidth]} {\externalfigure[spider.eps][width=.25\textwidth]} {\externalfigure[hacker.png][width=.25\textwidth]} {\externalfigure[mill.png][width=.25\textwidth]} \stopcombination \stoptext The first line has the images vertically centered, but the second line has them aligned to the top. Using "align=middle" made no difference. How could I get all lines with images vertically centered? Many thanks for your help, Pablo -- http://www.ousia.tk