When using multiple list-of on the same page they overlap

Question

When list-ofs follow each other they overlap, at least with my setup. Here's an example:

test.tex

\documentclass[a4paper]{memoir}

\usepackage{xltxtra}
\usepackage{polyglossia}

% New list of source code listings
\newcommand{\sourcename}{Source Code Listing}
\newfloat[chapter]{source}{los}{\sourcename}
\newcommand{\listsourcename}{List of Source Code}
\newlistof{listofsources}{los}{\listsourcename}
\newlistentry{source}{los}{0}

\renewcommand*{\insertchapterspace}{%
  \addtocontents{lof}{\protect\addvspace{10pt}}%
  \addtocontents{lot}{\protect\addvspace{10pt}}%
  \addtocontents{los}{\protect\addvspace{10pt}}}

\chapterstyle{pedersen}

\begin{document}

\frontmatter

\listoffigures

\listofsources

\mainmatter

\chapter{One}

\begin{figure} \caption{Some  fig} \end{figure}
\begin{figure} \caption{Other fig} \end{figure}

\begin{source} \caption{Some  src} \end{source}
\begin{source} \caption{Other src} \end{source}

\end{document}

Compile with:

xelatex test.tex && xelatex test.tex

This is the result:

I could add some vertical space, but is there a more correct way of handling this?

Answer 1

That's a side effect of the petersen chapter style. The definition of this style contains (among other things) the code line

\setlength{\beforechapskip}{-20pt}

which results in the observed overlap. One probably could add some safeguarding for the case of two unnumbered chapters starting on the same page, but IMO it's acceptable to manually add some vertical space in this case.