autoChange creating extra staff

[Alexandre Loomis]

Hi, I'm running into an issue using \autoChange. I'd like CrossStaff to share the lower staff (and upper with another voice, but that doesn't seem to cause any issues), but it's creating its own.

\version "2.24.0"

CrossStaff = \autoChange f {
  \relative c' {
    c2 c,
  }
}

VoiceTwo = \relative { \clef "bass" c,1 }

\new PianoStaff <<
  \new Staff = "up" {
    \new Voice \CrossStaff
  }
  \new Staff = "down" {
    \new Voice \VoiceTwo
  }
>>