parallelmusic problem: q-notation does not work in \relative

[Arno Waschk]

dear list,

the following

\version "2.15.4"
\parallelMusic #'(abc def) {
  <a c>2 q|
  <d f>2 q|
  % <a c>2 <a c>2 |
  % <d f>2 <d f>2 |
}

\new Staff {<<
    \relative c'' \abc
    \relative c' \def
    >>}


does not produce the desired result, since the second "chord" is one  
octave lower then the first.
it does work when processing the commented lines instead.

would be grateful for possible short-term workarounds, too.

cheers, arno