autochange sends voice to wrong clef

[snively]

% here is a case where autochange weirdly sends the top note to the
bass clef, using lots of ledger lines 

version "2.16.0"
score
{
 new
PianoStaff
 <<
 new Staff = "up" {
 <<
 new Voice {
 voiceOne

autochange
 relative c'' {
 r2 r4 e4 % problem case: both voices go to
base clef
 % r2. e4 % workaround
 }
 }

 new Voice {
 voiceTwo

autochange
 relative c {
 r2 r4 a4 % problem case: both voices go to
base clef
 % r2. a4 % workaround
 }
 }
 >>
 }

 new Staff = "down" {

clef bass
 }
 >>
}