"LaTeX3 Error: Command '\textsi' not yet defined!"

David Pesetsky pesetsk at mit.edu
Sat Feb 22 19:13:48 UTC 2020

FYI, I reported the bug to the developer, who replied:

Thanks. It looks like fontspec doesn’t define this any more. I’ll fix embrac. In the meantime you can add to your preamble


That should prevent the error.

Thank you for your help here.


On Feb 16, 2020, at 2:10 PM, David Pesetsky <pesetsk at mit.edu<mailto:pesetsk at mit.edu>> wrote:

One final note:  I have discovered that if I go to TexLive and change Configure > Change Default Tex Live Version from "TeXLive-2019" to "TeXLive-2018", the error and the "L3 Programming Layer" messages disappear.  I hope that narrows things down sufficiently.


On Feb 16, 2020, at 11:49 AM, David Pesetsky <pesetsk at mit.edu<mailto:pesetsk at mit.edu>> wrote:

Before (June 2019, via MacOS Time Machine):
LyX 2.3.2
TexLive 1.35
MacOS Mojave (10.14.x)

TexLive 1.36
MacOS Catalina (10.15.3)

Minimal Working Example:
without embrac package:
with embrac package:
<newfile3 produces error.lyx>

Without embrac, the file compiles successfully, but does display "L3 Programming Layer <date>" while compiling (as does every Lyx file at the moment).

Hope this gives you what you need to help, and many thanks in advance.


On Feb 15, 2020, at 11:24 PM, Joel Kulesza <jkulesza at gmail.com<mailto:jkulesza at gmail.com>> wrote:

On Sat, Feb 15, 2020 at 3:53 PM David Pesetsky <pesetsk at mit.edu<mailto:pesetsk at mit.edu>> wrote:
I was using Lyx for Mac rather extensively to write a long-ish manuscript about a year ago, but have been away from it for a while.

In the interval, a problem has arisen, though nothing has changed in my setup besides updating Lyx and Latex via TexLive.  I install the embrac package, which ensures non-italic brackets in otherwise italicized environments.  This used to work without a problem, but now generates the error message:

LaTeX3 Error: Command '\textsi' not yet defined!

I am sure of my trouble-shooting, since commenting out the usepackage command eliminates the error.

When I was using Lyx a year ago, I wasn't seeing any mentions of LaTex3, I'm fairly sure (and no errors from embrac).  Any idea what's going wrong and how I can eliminate the problem or work around it?


Additional details will be useful to folks if they wish to help.  For example, what versions of LyX and TeXLive were being used "before" and "after"?  What version of macOS were you using before and after?  Perhaps most important: please provide a minimal working example (MWE) [https://wiki.lyx.org/FAQ/MinimalExample] that demonstrates the problem now (and, ideally, that used to work before).


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