Why is there no auto beaming in temporary polyphony?

[Carl Sorensen]

< I'm not top posting

When I use temporary polyphony with the double backslash construct, autobeaming 
is not working for me.

%%%
\version "2.19"

  \new Staff = "right"{
    \clef treble
    <<{e''8 f''} \\ {a'4} >>  b'4 c'' b' |
    \voiceOne 
    e''8 f'' b'4 c'' b'
  }

%% 

I thought that the first voice in the double backslash construct got set as 
\voiceOne, but somehow in this example autobeaming doesn't work in the first 
measure, even though it does in the second measure.

I'm using Frescobaldi on OSX, Lilypond version 2.19.80.

Any ideas?

Thanks,

Carl