enumitem and description environment with classicthesis leads to compilation failure

[Former user]

If you load classicthesis and enumitem package (e.g. both without further options), and you use the description list environment the compilation will fail. E.g.

\documentclass[12pt,a4paper]{book}

\usepackage[]{classicthesis}
\usepackage{enumitem}

\begin{document}
\begin{description}
\item[hello] Hi
\item[what] why
\end{description}
\end{document}

leads to

! Missing number, treated as zero. } l.8 \item[hello] Hi A number should have been here; I inserted 0'. (If you can't figure out why I needed to see a number, look upweird error' in the index to The TeXbook.)*"

This is apparently caused by the "description" environment being re-defined twice: once by classicthesis and once by enumitem. For further information see here

The workaround is to load the classicthesis package with the "pdfspacing" option

\documentclass[12pt,a4paper]{book}

\usepackage[pdfspacing]{classicthesis}
\usepackage{enumitem}

\begin{document}
\begin{description}
\item[hello] Hi
\item[what] why
\end{description}
\end{document}

As further actions:

1. Fix the issue altogether, maybe detecting the enumitem package as specified in the Tex StackExchange discussion
2. Specify this conflict in the "Issues" section of the documentation (section 1.4)

[Ivo Pletikosić]

Hi Raffaele, thanks for your report. Starting from v4.4 microtype will be used for character spacing automatically with pdflatex as document processor. Until it's released later this month, please use the pdfspacing option.

[André Miede]

Thanks also from my side. As Ivo pointed out, this will be fixed in the next release (hopefully out soon!).