I don’t know if I use it wrongly, or it’s a bug in ConTeXt, but use \setuplist with numbercommand renders wrongly

% this is not working, ``chapter’’ and chapter name overlapped

\define[2]\ChapterNumber{chapter #1: #2}

% have to add extra spaces here to avoid overlapping

% \define[2]\ChapterNumber{chapter #1:\space\space\space\space\space\space #2}
\setuplist[section][numbercommand=\ChapterNumber]
\starttext
\completecontent
\section{blabla}
blabla
\section{blabla}
blabla
\section{blabla}
blabla
\stoptext

I use ConTeXt standalone with Mac OS X

mtx-context | ConTeXt Process Management 1.02
mtx-context |
mtx-context | main context file: /Volumes/DATA/ConTeXt/tex/texmf-context/tex/context/base/mkiv/context.mkiv
mtx-context | current version: 2017.12.04 16:37