Problem with repeat alternative endings that contain lyrics and leading rests

[Peter Heisen]

Dear List,

The LilyPond notation reference, section 2.1.2, (http://www.lilypond.org/doc/v2.18/Documentation/notation/techniques-specific-to-lyrics) contains the following example of how to use lyrics in concert with repeat alternative endings.  It compiles fine in version 2.18.2, showing both the first and second endings complete with lyrics:

\score {
  <<
    \new Staff {
      \time 2/4
      \new Voice = "melody" {
        \relative c'' {
          a4 a a a
          \repeat volta 2 { b4 b }
          \alternative { { b b } { b c } }
        }
      }
    }
    \new Lyrics {
      \lyricsto "melody" {
        Not re -- peat -- ed.
        \repeat volta 2 { Re -- peat -- }
        \alternative { { ed twice. } { ed twice. } }
      }
    }
  >>
}

In the following modified example, the first beat of each ending has been changed to a rest, and a syllable removed from the lyrics to match.  Now when compiled, it shows two first endings and two second endings.  Moreover the log contains the error "warning: already have a volta spanner, ending that one prematurely". I have scoured the documentation and searched the list archives, and cannot find any mention of this.  Can you help?

\version "2.18.2"

\score {

  <<

    \new Staff {

      \time 2/4

      \new Voice = "melody" {

        \relative c'' {

          a4 a a a

          \repeat volta 2 { b4 b }

          \alternative { { r b } { r c } }

        }

      }

    }

    \new Lyrics {

      \lyricsto "melody" {

        Not re -- peat -- ed.

        \repeat volta 2 { Re -- peat }

        \alternative { { twice. } { twice. } }

      }

    }

  >>

}

Thank you,

Pete H.