[NTG-context] braces removed in url

Dear list, I have the following sample: \setupinteraction[state=start] \starttext \startTEXpage[offset=1em] \def\MyURL#1{\goto{\hyphenatedurl{#1}}[url(#1)]} \MyURL{a={b}}\\ \MyURL{a=\letterleftbrace b\letterrightbrace}\\ \asciimode\MyURL{a={b}}\\ \stopTEXpage \stoptext For all three options, destination is a=#b. Both with MkIV and MkXL. What am I missing to get the destination a={b}? Many thanks for your help, Pablo -- http://www.ousia.tk