[NTG-context] Uppercase ssharp with XeTeX and LuaTeX

Hi, is there a solution for ssharp with XeTeX and LuaTeX, I have a word with a ß in it which I convert into uppercase letters and the ß remains a lowercase characters. This was no problem in the past with pdfTeX because it contained a SS character for this problem and the output is what I want but I have no solution for the other two engines. \starttext \WORD{Grußwort} \stoptext Greetings Wolfgang