[NTG-context] Overriding a chapter number

When I compile a chapter of a book separately, I want to override the automatic numbering because otherwise every separate pdf will have chapter 1. So I tried: \doifmode{standalone}{\setuphead[chapter][2]} \chapter[h:foo]{Foo} But the chapter still gets number 1 when I compile with texexec --pdf --mode=standalone c_foo.tex what am I doing wrong here? Thanks, G