extender line at lyrics doesn't work correctly

[Roland Goretzki]

> I'm not top posting.

% I'm sorry, but it seems unpossible to make it shorter!

% The following shows wrong behaviour of extender line:
% If the piano has notes faster than melody, extender line doesn't work,
% and if the piano has notes as fast as or less fast than melody,
% e. l. does work.

\version "2.10.11"
\layout { ragged-right = ##t }

melody = \relative c' { f2( g c1) }

text = \lyricmode { \small Oh! __ }

rechts = \context Staff \relative c'{
  d4 e f d c1
  %g1 c % incommenting this line and outcommenting the above will show extender
   line working well
}

links = \context Staff \relative c{ b2 g c,1 }

\score {
<<
  \new Voice = "mel" << \melody >>
  \new Lyrics \lyricsto mel \text

  \context PianoStaff
  <<
    \context Staff = "up" << \rechts >>
    \context Staff = "down" << \clef bass \links >>
  >>
>>
}