[NTG-context] comma as decimal separator in maths mode

Hi ... I am outputting some numbers in maths mode that have a comma as decimal separator. I get a big space after the comma, which I can prevent by writing $1{,}5$ Is there a less awkward way of getting the comma as a "real" decimal separator? Thanks, Martin \starttext $1,5$ \math{1,5} $1{,}5$ \stoptext