I had a working LaTeX file with biblatex referencing but after an update of the packages on July 3, 2022, including a package called biblatex-chicago my LaTeX code that worked yesterday produces the following 2 errors (from the log file):

! Package biblatex Error: Patching \MakeLowercase failed.
See the biblatex package documentation for explanation.
Type H <return> for immediate help.
l.212 \begin{document}
This is an internal issue typically caused by a conflict
between biblatex and some other package. Modifying
the package loading order may fix the problem.

There's another error that regarding \MakeLowercase.

I've tried going through the biblatex manual but can't find any \MakeUppercase or \MakeLowercase reference relevant to this error.

Any help appreciated as I am completely at loss

  • For information: I've reinstalled MacTex and my latex code works again. So I am pretty sure that one of the updates causes this error. I simply can't tell which one.
    – Harald
    Jul 3, 2022 at 14:26
  • 1
    It's a bug/incompatibility created by the last kernel update. Will be fixed Really Soon. (Just relying, I learnt about it in the chatroom).
    – Rmano
    Jul 3, 2022 at 14:45

2 Answers 2



The error should be resolved and original functionality should be restored in biblatex v3.18b and above if you use the LaTeX kernel at least 2022-06-01-PL5 and expl3 at least 2022-07-14.

If you are still experiencing this problem, update your TeX system thoroughly and completely.

Old answer

This is an issue caused by the new definition of \MakeUppercase and \MakeLowercase in LaTeX 2022-06-01-PL4 which landed in TeX Live on 2022-07-03.

An emergency update (biblatex v3.18a, see https://github.com/plk/biblatex/pull/1233) is available in TeX Live (it landed in TeX Live a day later on 2022-07-04, because the update deadline was narrowly missed).

If you update today, you should get a version of biblatex that no longer has this error.

Note that the emergency fix simply disables the patch, so it is theoretically possible that your document does not come out as desired, though I rather suspect that the patch is not relevant for the vast majority of users. See https://github.com/plk/biblatex/issues/1234 for progressing on re-enabling the patch.

  • Many thanks for this quick reply. This indeed resolves the issue.
    – Harald
    Jul 3, 2022 at 15:48

If it is 2023 and the answer of @moewe is not applicable. The error may be due to old biblatex config / style files in the local directory which apparently are no longer compatible with the current version of LaTeX.

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