quoteDuring midi

[Mogens Lemvig Hansen]

Hi List,

Music quoted with \quoteDirung does not make it to the midi file.  
Is this a known bug? 
- or possibly a feature?
- or a misunderstanding on my part?

\version "2.16.0"
soprano = \relative c'' { a2 b4 c d e f g  }
\addQuote "qsoprano" { \soprano }
mixture = \relative c'' {
 d4 d
 \quoteDuring "qsoprano" { s2 s2 }
 d4 d
}
\score{ 
 \mixture
 \midi {}
 \layout {}
}

Regards,
Mogens