[XeTeX] xunicode combining ring above

[Lasse Bombien]

Dear list,

something goes wrong when I use the TIPA part of xunicode:
\r{x} doesn't give me an x with a ring above it but an x with a cedilla below. Direct
Unicode input works fine.
It doesn't seem to be a font problem as I tried several fonts.
Below is a minimal example. Does anyone have an idea?

Lasse

\documentclass[12pt]{article}
\usepackage{fontspec}
\setmainfont[Ligatures=TeX]{Linux Libertine O}
\begin{document}
Tipa input: \textipa{ba\r Nkan}\\
unicode input: baŋ̊kan
\end{document}