Error with package diffcoeff

Question

When loading the diffcoeff package, even in very basic examples, I'm getting a repeated error that wasn't there a few weeks ago. Does anyone know what the problem is? Thanks!

Here is the MWE:

\documentclass[letterpaper,12pt]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage[italian,english]{babel}
\usepackage{diffcoeff}
\diffdef {}
{
    op-symbol    = \mathrm{d},
    op-order-sep = 0 mu
}
\begin{document}

Some text.

\end{document}

And here is the error:

/usr/local/texlive/2022/texmf-dist/tex/latex/diffcoeff/diffcoeff.sty:138:
Illegal parameter number in definition of \key code > 
template/derivative/DERIV/long-var-wrap/dv.
<to be read again> 
                   2
l.138   } 

Answer 1

I couldn't reproduce the error until an xtemplate update this morning. I've amended diffcoeff following a suggestion from Joseph Wright and uploaded the revised version (4.1) to CTAN a few minutes ago.

Answer 2

In case you don't know how to fix this problem, download diffcoeff.zip from CTAN (version 4.1), unzip it, and copy diffcoef.sty in the folder you are working (the one that has your main tex file). Let's hope CTAN is going to be updated soon with the last version.