Tie like a slur

[Phil Holmes]

I've been setting some music with something like the following:

<<
\new Staff {
 \time 6/8
 \clef "treble"
 a''8 a''8 a''8 a''8 a''8 a''8
}
\new Staff {
 \time 6/8
 \clef "bass"
 \voiceOne
 < a c' f'>4. ~  < b c' e'>4.
}
> >

(I've done the 2 staves because it gets the spacing on the lower one closer 
to what I have).

Lily sets this as shown in the attached image - to my eyes this looks more 
like a slur than a tie.  Bug?  Issue 139?

--
Phil Holmes
Bug Squad

TieLikeSlur.png
Description: PNG image