I've been using the fixltx2e package for a while, with a tweak described here on the site. Recently, this has gotten me the following error message:

Package fixltx2e Warning: fixltx2e is not required with releases after 2015
(fixltx2e)                All fixes are now in the LaTeX kernel.
(fixltx2e)                See the latexrelease package for details.

How do I robustly make sure fixltx2e is used exactly when necessary?

  • 2
    Just ignore the warning, if you plan to use the same document with pre 2015 kernels. Otherwise remove \usepackage{fixltx2e}.
    – egreg
    Jan 11, 2016 at 21:19
  • 2
    Since it's just a warning, you can silence it: \usepackage{silence} \WarningFilter{fixltx2e}{}.
    – Werner
    Jan 12, 2016 at 1:07
  • @Werner If you're already turning off all the warnings for a given package non-selectively, you might as well use the command designed to do just that: \WarningsOff[fixltx2e]. Note that either way, this command needs to be placed BEFORE you load the fixltx2e package (using \usepackage{fixltx2e} or \RequirePackage{fixltx2e}) for it to work!
    – Brunox13
    Jul 29, 2021 at 0:18

2 Answers 2


You can distinguish pre-2015 kernels from the fact that \IncludeInRelease is not defined:

\expandafter\ifx\csname IncludeInRelease\endcsname\relax

See What does \begingroup\expandafter…\endgroup do? for an explanation of the code.

  • Why aren't lines 2-4 in your snippet sufficient? You kind of lost me with the first line.
    – einpoklum
    Jan 11, 2016 at 23:37
  • 1
    @einpoklum Omitting the first line would leave \IncludeInRelease defined to be equivalent to \relax, if previously undefined. With the first line, the \csname construction is performed when the group has not yet been closed. When \endgroup performs its actions (which include removing the previous setting of \IncludeInRelease, if done). See tex.stackexchange.com/questions/24393/…
    – egreg
    Jan 11, 2016 at 23:40
  • Also, why not use something like \ifcsname?
    – einpoklum
    Jan 12, 2016 at 0:12
  • 2
    @einpoklum If your aim is to make the code compatible with older releases of TeX, you can't assume e-TeX.
    – egreg
    Jan 12, 2016 at 0:20

If you are using TeXLive you can use the solution below to obtain which version you are running.





    \typeout{*** Included fixltx2e}
    \typeout{*** DId NOT Included fixltx2e}

  • 1
    er why not just use \fmtversion ? Jan 11, 2016 at 22:45
  • @DavidCarlisle: Sorry, did not know about \fmtversion. Jan 11, 2016 at 22:50
  • 1
    \@ifl@t@r\fmtversion{2015/01/01}{yes}{no} :-) Jan 11, 2016 at 22:56
  • Ah, but I can't assume I use TeXLive, now can I...?
    – einpoklum
    Jan 11, 2016 at 23:36

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