Slur bug in 2.8.3

[CSÉCSYLászló]

I have a volta-style repeat, which ends on a slur's start. Both (every)
alternative should have the end of the slur, which I can't set out with lily
2.8.3; looks like every slur-start should have exactly one slur-end. I have two
choices: one slur for the first alternative, and nothing for the second; or
slur-end for the second, but this way it's set out as one long slur above the
whole first alternative, which is wrong.

Here is an example with the second choice mentioned above.

\version "2.8.3"
\score { <<
\new Staff = uni <<
\new Voice = "unisono" {
\relative c''
\repeat volta 2 { a1( | }
\alternative { { a2 r2 } { g2) b4 a | g2 r2 } }
\bar "|." } >> >> }

How should I set this out correctly? Is there any way to workaround this?

Thx, Boobaa