Problem getting syllables onto tied note across bar end

[Henry Law]

I am having a problem getting my lyrics to fit across a group of notes 
which contain a tie.  Here's the smallest possible example:

\version "2.16.2"
melody = \relative c'' {
  \clef treble
  \key a \major
  \time 4/4
  b8. b16          b16 cis8 a16~  a8. e16        fis8 a16 ( a~ |
  a8 fis )         r4             r2                           |
  r2                              r4             r8 a16 a      |
}
text = \lyricmode {
  da    da  da  a da a -- one  two three
}
\score {
  <<
    \new Voice = "mel" {  \melody }
    \new Lyrics \lyricsto mel \text
  >>
  \layout {
    \context { \Staff \RemoveEmptyStaves }
  }
}

The way I coded it, the syllable "three" is intended to fall on the last 
A (16th) of the first bar and run over the a8 fis of the next bar.  But 
as can be seen in http://www.lawshouse.org/music/problem01.pdf the slur 
doesn't start on the last 16th but on the previous one, and the syllable 
"two" is assigned to the three A's and the F#, leaving the syllable 
"three" to match up with the 16th A's after the rests.

What am I doing wrong?

--

Henry Law            Manchester, England