here's my thesis Latex files: http://www.mediafire.com/download/c7q8z4v6gv864rk/triet_thesis_clean.rar

Please help me to fix the error, I've tried all the things I can find with Google :( :

   ! Missing \endcsname inserted.
   <to be read again>
   l.52 ...}intopreamble]Deobfuscation}{{4.1.1}{xii}}
   The control sequence marked <to be read again> should
   not appear between \csname and \endcsname.
  • 4
    Please show use some code (Minimal working example).
    – Johannes_B
    Nov 26 '13 at 16:09
  • 2
    On overleaf, I just deleted the cache and aux and other files. It solved the problem.
    – imsrgadich
    Sep 22 '18 at 17:39

You have a wrong character in one of your labels:


where, between LLVM and Deobfuscation, you have the Unicode character U+200E (LEFT-TO-RIGHT MARK) that somehow sneaked in.

Retype the label and you should be OK.

  • 18
    Thank you. I really appreciate your help. Could you tell me how you find out the reason :) ? Nov 26 '13 at 17:37
  • 13
    If you use the \usepackage{underscore} the '_' character in labels will cause this error. To fix this also use \usepackage[english]{babel}
    – Cyrille
    Dec 7 '15 at 12:07
  • I'm stuck with this error message, and I would love to know how I go about fixing it? Mar 28 '18 at 15:14
  • @AndreasStorvikStrauman Difficult to say without an example.
    – egreg
    Mar 28 '18 at 15:50
  • 2
    @AndreasStorvikStrauman I copied the offending text and pasted on a multiconverter that shows every byte, for instance r12a.github.io/app-conversion
    – egreg
    Mar 28 '18 at 17:21

For others if you have not tried to delete all the generated files from pdflatex and bibtex, then do that before any other changes, because it could be a compilation error.


I never wrote Vietnamese and don't know if it can be done with pdflatex. However, if I use xelatex instead and

%\usepackage[utf8x]{vietnam}%% xelatex is by default utf8
\usepackage{fontspec}%% load unicode fonts

I'll get a proper output with out any errors.

  • 1
    Unfortunately, I have to write my thesis in Vietnamese :( . Could you help me a little bit further? Nov 26 '13 at 16:36
  • as I wrote: use may preamble and then run xelatex instead of pdflatex. Every editor ahopuld have such a button or topix for xelatex
    – user2478
    Nov 26 '13 at 16:41
  • 1
    No, the OP probably won't get proper output: the error is caused by a spurious (invisibile) character in a label and probably all references to it will not be resolved.
    – egreg
    Nov 26 '13 at 17:45
  • I get all references right with xelatex
    – user2478
    Nov 26 '13 at 18:29
  • 1
    You get references right provided you build \ref{...} by copy-pasting from the argument of \label. If you type directly \ref{subsec:LLVMDeobfuscation} you can't get a correct reference.
    – egreg
    Nov 27 '13 at 11:17

If you use \usepackage{underscore} the '_' character in labels will cause this error.

To fix this add the following: \usepackage[english]{babel}

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