# Hyperref warning when combined with package titlesec [duplicate]

How can one get rid of the hyperref warning about the $ signs in the subsection title that are generated in the following minimal example? \documentclass{book} \usepackage{titlesec} \usepackage{titletoc} %\newcommand{\subsecformat}[1]{\parbox[b]{\linewidth}{ % \normalsize\selectfont % \filright\textcolor{black}{\textsc{#1}}}} \usepackage{hyperref} \begin{document} \subsection{Can light move faster than$c$?} No. \end{document}  Probably the command \subsecformat needs to be improved. How should this be done? • This has nothing to do with titlesec. Use \texorpdfstring{$c$}{c} or ignore the warning. By the way, defining \subsecformat does exactly nothing. – egreg Jan 20 '15 at 18:29 • Just for completeness, the answer is to write \texorpdfstring{$c\$}{c} in the title, in order to get the PDF bookmarks right. – Motion Mountain Jan 22 '15 at 9:57