I try to compile the following code with luatex

\usepackage[margin=2.5cm]{geometry} % for margins on a A4paper
\usepackage[Export]{adjustbox} % #124
Sample text%

and get the following exception:

Package luatex.def Info: images/6195f2d3c08c94fdc73f8d014f5614648c81ee8b.png  u
sed on input line 3.
(luatex.def)             Requested size: 1259.70319pt x 917.42528pt.
! Undefined control sequence.
\the@chapter ...ed \relax \else \ifnum \c@chapter 
                                                  >\z@ \thechapter \fi \fi 
l.11 \caption{
The control sequence at the end of the top line
of your error message was never \def'ed. If you have
misspelled it (e.g., `\hobx'), type `I' and the correct
spelling (e.g., `I\hbox'). Otherwise just continue,
and I'll forget about whatever was undefined.

I've publish the log file under https://justpaste.it/cvwv5

I think its somehow related with latvian but I'm not sure. Changing to e.g. french compiles.

1 Answer 1


Not sure why you load bidi=basic for a Latvian document. Anyway, that's not the problem.

If you try minimizing the example starting from



\caption{Sample text}


you'll see no error. But upon adding titlesec the error appears. If we comment out the call to babel, the error disappears again.

Thus the problem is in compatibility with babel-latvian and titlesec.

What happens? In latvian.ldf we find

111 \gdef\the@chapter{%
112   \ifx\chapter\undefined\relax\else
113   \ifnum\c@chapter>\z@\thechapter\fi\fi}
165 \def\thefigure{\the@chapter\@arabic\c@figure.}

(line numbers just for reference) which is the cause of the problem, because titlesec does

\expandafter\ifx\csname chapter\endcsname\relax

Testing for \chapter being undefined should always be


An alternative possibility is

\ifcsname chapter\endcsname <true>\else<false>\fi

that wouldn't make chapter equivalent to \relax like the code currently used by titlesec does.

However, \ifx\chapter\undefined is definitely not the best idea.



%%% ensure \chapter passes the \ifx\chapter\undefined test


\caption{Sample text}

  • Thx for the detailed analysis. I'll test tomorrow. When I read it properly than that's a bug in the package titelsec, right? Or should this be fixed in Babel? More the question where to raise an issue
    – LeO
    Sep 25 at 19:01
  • The bidi option is more as some kind of fallback if we include Arabic text. Won't apply for the MWE.
    – LeO
    Sep 25 at 19:04
  • @LeO In my opinion it should be fixed in both.
    – egreg
    Sep 25 at 19:47
  • I've also filed a ticket for Babel (github.com/latex3/babel/issues/264). Just to clarify, the \let\chapter\undefined command makes sure that \chapter is defined somehow. Does it have any negative effect if I leave it there, e.g. for other languages that have no problems? Or simpler: Can I leave the command in general without any negative impact?
    – LeO
    Sep 26 at 6:53

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