[tex-live] Problem with unicode math?

[Herbert Schulz]

Howdy,

I get thee following error when using unicode-math 0.5e (fully updated TL2011):

/usr/local/texlive/2011/texmf-dist/tex/latex/unicode-math/unicode-math.sty:105:
 Undefined control sequence.
l.105 \xetex_or_luatex:nnn
                           { \cs_new:Npn \um_cs_compat:n #1 }
? 

when compiling the file

%%!TEX TS-program = xelatex
%%!TEX encoding = UTF-8 Unicode
\documentclass{article}
\usepackage{fontspec}
\setromanfont[Ligatures=TeX,Numbers=OldStyle]{XITS}
\usepackage{unicode-math}
\setmathfont{XITS Math}
\begin{document}
Here is an equation: \(x^{2}+y^{2}=z^{2}\).
\end{document}

Clearly the problem is happening while loading unicode-math.

Good Luck,

Herb Schulz
(herbs at wideopenwest dot com)