According to the accepted answer of this question TeX never hyphenates words that already contain a hyphen. Nevertheless in a document here I find that the word “Modula-2” is hyphenated, as the following image shows (generated with this file using XeLaTeX, version 3.1415926-2.4-0.9998 (MiKTeX 2.9 64-bit)).
\documentclass[10pt]{article}
\begin{document}
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Vestibulum Modula-2
nisi urna, congue sed congue id, iaculis et lacus.
\end{document}

Apparently I can’t use \hyphenation to prevent this; but the word appears several times so I don’t want to use \mbox either. Is there a better solution?
