[NTG-context] yscale not working

Why is there no effect of the yscale parameter in \externalfigure when the width-parameter is given? In the MWE it is the intention to stretch the height of the figure by a factor of two. But nothing happens. Leaving out the width does stretch the height, but then it becomes too wide. \starttext Test \tex{externalfigure} scaling - \ConTeXt\ \contextversion \blank \type{\externalfigure[test][width=0.50\textwidth]}\crlf \externalfigure[test][width=0.50\textwidth] \blank \type{\externalfigure[test][width=0.50\textwidth,yscale=2000]}\crlf \externalfigure[test][width=0.50\textwidth,yscale=2000] \stoptext dr. Hans van der Meer