completion_heads_engraver is missing a note

[andy]

> I'm not top posting.


when rendering the example below the whole note is not rendered correctly:
it appears as a dotted 1/4 in the first measure: that is ok.
it appears as a 1/2 in the second measure: there is missing an 1/8.
ie. the second measure contains a 1/2, an 1/8 and 1/4 ie. an 1/8 is missing.

\version "2.10.25"
\new Voice \with {
  \remove "Note_heads_engraver"
  \consists "Completion_heads_engraver"
}
{
c'2 d'8 c'1
d'8 c'4
}