ChoirStaff produces DrumStaff in 2.5.30

[Imruska]

Hi,

As I was trying to make some (very nice, of course) choral music score 
with 2.5.30, in which at the \score part I put
\context ChoirStaff <<
... >>
Lilypond tells me at Interpreting Music:

lumen_ad_revelationem.ly:14:8: warning: junking event: `KeyChangeEvent'
        \key f \major

four times (i.e once for all parts, since the music is in 4 parts), and 
the result is a Drum score, without keys, and only one line instead of 
five, i.e. without pitches, only with rhythm and lyrics.

In 2.4.x this worked fine.

I think this has to be fixed before 2.6.0

Pothárn Imre