lilypond-book linewidth: unwanted space at the left of the Staff

[Robert Memering]

Dear all,

I have the following problem with the line-width parameter used by 
lilypond-book:
When I specify the line-width to be exactly the same as my LaTeX 
\textwidth, the resulting small generated PDFs which are embedded have 
the right size, but there is some unwanted empty space at the left of 
the Staff, making the actual line of music a little smaller. I would 
rather have the Staff be of exactly the specified width. By the way, the 
result is the same when lilypond-book guesses the line-width automatically.

I'm using Lilypond 2.12.2, with the following commands:

lilypond-book --pdf --format=latex --latex-program=pdflatex minimal.lytex
pdflatex minimal.tex

Here is a small example lytex:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
\documentclass{article}
\setlength{\textwidth}{100mm}

\begin{document}

\begin[line-width=100\mm]{lilypond}
  \relative c' { c c c c c c c c c c c c c c c c }
\end{lilypond}
\rule{\textwidth}{1pt}

\end{document}
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Thanks in advance for any help,
best regards,
Robert Memering