Percent repeats in lyrics causes error in 2.18.2

[a . n . vinogradov]

I've entered some repeated music and folded it with 'repeat percent' in
the score.
However, lyrics doesn't understand the repetition, so adding
\unfoldRepeats caused messing between music and lyrics.
I've added same 'repeat percent' to the lyrics pieces then. It works
perfectly when unfoldRepeats is active!

But happend when I removed 'unfoldRepeats'. Piece of percents
immediately crashed lilypond internals with error:

Interpreting
music...[8][16][24][32][40][48][56][64]/usr/share/lilypond/2.18.2/scm/m
usic-functions.scm:319:21: In procedure car in expression (car durs):
/usr/share/lilypond/2.18.2/scm/music-functions.scm:319:21: Wrong type
(expecting pair): ()

Wrong fragment caused error looks like:
%\lyricmode {
...
\repeat percent 2 { Di -- es, di -- es i -- ræ. }
...
%}

The objective here is that it would be good to have a kind of repeat
(for lyrics) which just show the content once being 'compressed', but
repeat it when being unfolded, without any other side effects.
Volta repeat doesn't work, because it causes repetition marks to be
injected into the score (yes, even being applied just to the lyrics; it
is maybe another bug).
Percent repeat also doesn't work, but causes even worse stopper error,
then just unusual output.