[XeTeX] wrong uccode of ß

[Ulrike Fischer]

Hello,

in the following document I get in both cases the result "SCHLIEßEN"
instead of the expected "SCHLIESSEN". (Uppercase of ß is SS, I don't
know if Unicode somehow distinguish between a SS with lowercase ß and a
SS with lowercase ss). 

It doesn't matter if I load ngerman or not. As far as I can see the
uccode is set in unicode-letters.tex. 

\documentclass[a4paper]{article}
%\usepackage[ngerman]{babel}
\usepackage{xltxtra}

\begin{document}
\MakeUppercase{schließen}
\uppercase{schließen}
\end{document}

-- 
Ulrike Fischer