[NTG-context] Letter backaddress

Dear Wolfgang, I'm struggling with the backaddress option … I tried the following code --- \usemodule[letter] \starttext \setupletter [fromname={Arthur Thor}, fromaddress={Hidden Street 2\\57895 Mysterytown}, backaddress={Arthur Thor, Hidden Street 2, 57895 Mysterytown}] \setupletter [toname={Mike Willson}, toaddress={Lindenstreet 12\\78569 TeX City}] \startletter [subject={Step by step guide to writing a letter}, opening={Dear Reader,}, closing={Greetings from the Author}] \input knuth \stopletter \stoptext --- but couldn't see the backaddress line in the output. What do I have to change? Best wishes, Oliver