[NTG-context] Argument of \startInvoice has an extra }.

Hi, How could I avoid that error here please: --8<---------------cut here---------------start------------->8--- \def\beginInvoice{\dosingleempty\dobeginInvoice} \def\dobeginInvoice[#1]{\grabbufferdata[myLetter][beginInvoice][endInvoice]} \def\startInvoice#1\stopInvoice{bla} \starttext \beginInvoice \startInvoice test \stopInvoice \endInvoice \stoptext --8<---------------cut here---------------end--------------->8--- TIA for any help, -- Peter