Comment 2 for bug 714213

It's not really that 'the file contains' but rather 'the file name contains'.
The same issue goes for the convert-ly utility.

A patch by Jan Nieuwenhuizen is now available, see
  http://lists.gnu.org/archive/html/bug-lilypond/2011-03/msg00322.html
It has been tested and It will be applied upstream very soon