[NTG-context] Vanishing chapter title from Contents

Hi, maybe, codes is our language :-) % define a new head\definehead[backmatterchapter][chapter] \starttext \startfrontmatter \title{Preface} \completecontent \stopfrontmatter \startbodymatter \chapter{First Chapter} \stopbodymatter \startbackmatter \backmatterchapter{Backmatter} \stopbackmatter \stoptext The chapter title "Backmatter" in the backmatter won't appear in the Contents. Why? How can I make it appear in the Contents? Best regards,Tim