Using \ExplSyntaxOn breaks \xpatchbibmacro. Can this be fixed, or will I just need to use xpatch commands elsewhere?




  author    = {John Smith},
  title     = {Some Random Thing},
  date      = {1970}
  author    = {John Smith and Bob Smith},
  title     = {Some Other Thing},
  date      = {1971}

\ExplSyntaxOn % Removing this fixes it...
\xpatchbibmacro{date+extradate}% Remove date's parentheses, add period before (/a/428193)

  • What's the reason for \ExplSyntaxOn?
    – egreg
    Aug 13, 2020 at 11:45
  • In my document I'm using it for l3keys, and there's a lot of conditional groups. \ExplSyntaxOn can't be put into groups, which forces me to split and double my conditionals. Aug 13, 2020 at 11:47
  • That's expected. Patching relies on everything having the “right” catcodes, and enabling expl3 syntax changes quite a few of them, so patching breaks. For example, if a command contains a ~ and then you patch it, it becomes a space in expl3 syntax. Aug 13, 2020 at 11:49
  • @TakingItCasual An example of what you need would be useful (in a new question).
    – egreg
    Aug 13, 2020 at 12:51

1 Answer 1


\ExplSyntaxOn changes the category code of several characters (space, :, _, ~) and the patching routine may fail if the category codes are different from those at definition time.

Don't use \xpatch... under the scope of \ExplSyntaxOn.

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