[NTG-context] Headers and footers in backmatter

Dear all, I have noticed that when I set my index as a \chapter within the \startbackmatter...\stopbackmatter structure of a document, my headers and footers, including page numbers, disappear. Even the backgrounds disappear. The only commands I can find which seem to influnce the sectionblock behaviour are \setupsectionblock and \setupsection, but neither of these has a setting for page numbering or headers/footers. Looking through the sources hasn't helped me either. Can anyone shed any light on the mechanism for adjusting this behaviour? Thanks Duncan