Percent repeat counter in Staff with ChordNames

[Robert Schmaus]

Dear Lilyponders,

I have the following problem: Within a staff of "normal" written music, 
I include chord names to indicate improvised/soloing passages. If a 
chord is repeated over a large-ish number of bars, I'd like to use 
percent repeats and possibly the counter, too.
But I can't get the counter to work:

%%%%%%%%%%%%%%%

\version "2.19.18"

\score {

  \new Staff
  \with {
    \accepts "ChordNames"
    \consists Percent_repeat_engraver
  } {
    % some written out music
    c''4 c'' c'' c''

    % switch to changes
    \chords {
      \set countPercentRepeats = ##t
      \set repeatCountVisibility = #(every-nth-repeat-count-visible 4)
      \repeat percent 8 { c1 : maj7 }
    }
  }
}

%%%%%%%%%%%%%%%%

Everything works fine except the Percent Repeat Counter. If I switch 
from \chords { ... } to \chordmode { ... }, the counter works, but I no 
longer get ChordNames but stacked notes.

Is something missing from the \with { ... } statement?

Any help appreciated!
Peaceful days to everyone,
Robert