code produces pdf but fails for svg

[Gerard McConnell]

Hello,
The following is a chord sheet which I'll need to edit in Inkscape.
Lilypond produces the pdf fine, but when I use "%lilypond -dbackend=svg %buffer"
the message is "<unnamed port>: In _expression_ (repeat-slash 2.0 1.0 ...):
<unnamed port>: Unbound variable: repeat-slash"
What am I doing wrong?
Thanks for any help,
gerard

sl = \repeat percent 2 {s1}
\score {
    <<
         \chords {
         g1 \bar ":|"
         
         g g:maj7 g:7 g:7 c c ees ees
         e:m dis:5+ g/d a
         a:m a:m d:7 d:7
         g g b b e:m g/d c c:m g g
         
         g a:m g/b c g/d d:7 c c g g 
             }
     {
     \key bes \major
     \numericTimeSignature
     \time 4/4
     s1 s s \sl \sl \sl \break
     \repeat volta 2 {s1 s s s}
     \sl \sl \bar "||" \break
     \bar "|:" \sl \sl s1 s s s \bar ":|"
     \sl \bar "||"  \break

     s1 s s s s s \sl \sl \bar "|."
     }
 >>
}