[NTG-context] Stray blank page with part

Dear list, Motivated by https://tex.stackexchange.com/questions/406892 I wanted to disable page breaks for parts.  This works on all pages, except the first page of a document.  Why?  MWE is below as always.  Reproducible with TL 2017 and latest beta. Cheers, Henri \setuphead   [part]   [page=no] \starttext \startpart[title=Part One]   \startchapter[title=Chapter One]   \stopchapter   \startchapter[title=Chapter Two]   \stopchapter \stoppart   \startpart[title=Part Two]   \startchapter[title=Chapter One]       \stopchapter   \startchapter[title=Chapter Two]   \stopchapter \stoppart \stoptext