I have a problem in enabling tracking of small caps [whether the font has small caps or not] when I load french babel plus microtype. The problem appears only in my titles for the section and only when those titles have some characters !, » and perhaps others. If I disable the tracking from microtype, all goes well.

LuaTeX error /texmf-dist/tex/generic/babel-french/frenchb.lua:66: attempt to index a nil value. \section{SSS! » !}

Here is a extract from the manual of frenchb, at page 38, which says that babels tweaks the small caps :

\bsc: As family names should be written in small capitals and never be hyphenated, we provide a command (its name comes from Boxed Small Caps) to input them easily. Note that this command has changed with version 2 of frenchb: a \kern0pt is used instead of \hbox because \hbox would break microtype’s font expansion; as a (positive?) side effect, composed names (such as Dupont-Durand) can now be hyphenated on explicit hyphens. Usage: Jean~\bsc{Duchemin}.

\DeclareRobustCommand*{\bsc}[1]{\leavevmode\begingroup\kern0pt \scshape #1\endgroup}

I have no error when lualatex compiles with microtype without babel and I do not have errors when only babel is present. There is no error with microtype+babel **if I do not redefine my section with \scshape.**

I need polyglossia because I have other languages with peculiar fonts,. I have no error when I disable tracking in microtype, but still keep babel+polyglossia+microtype... plus my definition of \section

This is the tex file

\documentclass[oneside,a4paper, 12pt]{article}


\setmainfont{TeX Gyre Termes}


\@startsection {section}{1}{0em}{0\parskip}{1cm}{%

\SetTracking{encoding={*}, family= *, shape=sc}{33}


\section{SSS! » !}


closed as unclear what you're asking by Andrew Swann, Bobyandbob, Troy, Stefan Pinnow, CarLaTeX May 15 '18 at 10:35

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  • 3
    It makes no real sense to use babel together with polyglossia. However, tracking doesn't work with xelatex and TeX Gyre Termes has no bold Small Caps. – user2478 Dec 31 '15 at 9:59
  • 1
    With fontspec, you can use a command like this: \addfontfeature{LetterSpace=20.0}. – Bernard Dec 31 '15 at 13:59