Various documents mention a namespace feature for references by setting prefix=+. This is a really cool feature but I cannot get it to work. Why does the following example not work:
\setupinteraction[state=start]
\setuphead[chapter][prefix=+]
\starttext
\startchapter[reference=chap1,title={First Chapter}]
\startsection[reference=sec1,title={First Section in First Chapter}]
Reference \type{sec1} is \about[sec1].\par
Reference \type{chap2:sec1} is \about[chap2:sec1].\par
\stopsection
\stopchapter
\startchapter[reference=chap2,title={Second Chapter}]
\startsection[reference=sec1,title={First Section in Second Chapter}]
Reference \type{sec1} is \about[sec1].\par
Reference \type{chap1:sec1} is \about[chap1:sec1].\par
\stopsection
\stopchapter
\stoptext
Any help is appreciated.