problem in midi file

[Pascal Legris]

I have a problem with midi generated files.
After a tie, notes at the same pitch than the tie are shifted to the 
left in the midi file.

\paper {
    linewidth = 160 \mm
}
\renameinput "miditest.ly"

\version "2.1.32"

\header {
}


\score {
  \notes\relative c'' {
    \time 4/4
    c1 ~ c4 b c d
  }
  \paper{ raggedright = ##t }
  \midi { \tempo 4 = 110 }
}


in the resulting midi file, the last c is shifted to the left :


@+,
Pascal Legris