# xelatex error paragraph ended before \@tempa was complete

Hi I ve got this error message

Runaway argument?
\x@protect $\protect \[ \@nil \@ifpackageloaded {amstex}{\def \@tempa \ETC. Paragraph ended before \@tempa was complete. <to be read again> \par l.435 \newenvironment{proof}[1][\proofname]{\par  while compiling this in XeLaTex \documentclass[12pt]{book}%thesis \usepackage{polyglossia} \setmainlanguage{english} \usepackage[numbers]{natbib} \usepackage{amsfonts} \usepackage{amsthm} \usepackage{amsmath} \usepackage{amssymb} \usepackage{makeidx} \usepackage{graphicx} \usepackage{epigraph} \usepackage{pdfpages} \usepackage{url} \usepackage{breqn} \usepackage{setspace} \usepackage{dsfont} \usepackage{eurosym} \usepackage{epstopdf} \usepackage{color} \usepackage{setspace} \usepackage{titling} \begin{document} bla \end{document}  What seems to be the pbm? ## 1 Answer polyglossia (or a package it loads) makes \[ robust but amsthm isn't expecting that. If you reset the original definition, things work better, \documentclass[12pt]{book}%thesis \let\zz\[\let\zzz$
\usepackage{polyglossia}
\let$\zz\let$\zzz

\usepackage{amsthm}

\begin{document}
bla
\end{document}


(I removed redundant packages from the example)

• David, it works. The original definition of what does the combination of \let\zz[\let\zzz] reset? – agozar Aug 28 '13 at 15:38
• @agozar it saves the definition of $ in \zz and $ in \zzz (the z names are just arbitrary local names) and then restores them after polyglossia, setting $ back to \zz which is its original definition, and same for $ – David Carlisle Aug 28 '13 at 15:46
• @ggll that isn't a comment anyone can act on. Which packages? Also which format as the situation has changed since this answer, latex now makes \[ robust by default. Probably best to ask a new question on teh sit ewith a complete example that shows the problem rather than comment on an old answer. – David Carlisle Sep 16 '15 at 15:39
• getting the same error without using polyglossia: solved by loading amsthm after amsmath as advised here: tex.stackexchange.com/questions/164892/… – ggll Sep 16 '15 at 15:46