Cross staff stems with modern flags

[Andrew Bernard]

Greetings List,

If I have modern straight flags turned on and attempt to use cross-staff stemmed chords, the flags show up on the bottom stems. What am I doing wrong? Using ordinary default flags, the problem is not visible.

\version "2.17.18"

upper = \relative c'' {
  \clef treble
  \voiceOne
  a8 d e f
  \oneVoice
  c d e f
}

lower = \relative c {
  \clef bass
  \voiceOne
  \autoBeamOff
  \crossStaff { e8 d e f }
  \autoBeamOn
  \oneVoice
  g8 f g4
}

\score {
  \new StaffGroup <<
    \new Staff { \upper }
    \new Staff { \lower }
  >>

  \layout {
    \context {
      \Score
      \override Flag #'stencil = #modern-straight-flag
    }
    \context {
      \StaffGroup
      \consists #Span_stem_engraver
    }
  }
}

Andrew