# Roman number in chapter header but not in TOC

I need roman numbers for chapters header but in the table of contents I still want arabic numbers for the chapter. Is it possible?

For the chapter header I used this tag:

\renewcommand{\thechapter}{\ \Roman{chapter}}


Thanks a lot

• Welcome to LaTeX! Welcome to TeX.SX! Please make your code compilable (if possible), or at least complete it with \documentclass{...}, the required \usepackage's, \begin{document}, and \end{document}. That may seem tedious to you, but think of the extra work it represents for TeX.SX users willing to give you a hand. Help them help you: remove that one hurdle between you and a solution to your problem. – Moriambar May 17 '17 at 19:23
• Is the \  really necessary there? – user31729 May 17 '17 at 19:33

With the following code, the \renewcommand you're using now is not needed (and should in fact be omitted to obtain arabic numbers in the table of contents).

\documentclass{book}
\usepackage{etoolbox}

\makeatletter