autochange with multiple voices

[Nik Repka]

> I'm not top posting.

I am attempting to make a scales sheet for piano.  I need to use autochange
simultaneously in two voices.  

I am using the syntax from this snippet page:
http://www.lilypond.org/doc/v2.15/Documentation/snippets-big-page#keyboards-using-autochange-with-more-than-one-voice.

The issue I am having is that autochange only works on the top voice, and it
drags the lower voice up into the top staff.  Here is the code:

\version "2.18.2"

scaleRH = \relative c' {c d e f g a b c c b a g f e d c
g a b c d e fis g g fis e d c b a g}

scaleLH = \relative c {c d e f g a b c c b a g f e d c 
g a b c d e fis g g fis e d c b a g}


\score {
   \new PianoStaff 
    
      << \new Staff = "up"
         <<
           \new Voice {
           \voiceOne
           \autochange
    
           \scaleRH 
           
           }

           \new Voice {
           \voiceTwo \autochange 

           \scaleLH 
           }
         >>

      \new Staff = "down" { 
          \clef bass
      }
      >>
}