Barnumbers alignment

[Marco Caliari]

In lilypond 1.5.58 barnumbers hit the StaffGroub bar at each row. 
Example:

papersize="a4"
\include "paper20.ly"
\score{
\notes{
<\context StaffGroup = duo
<\context Staff = StaffA{...} 
 \context Staff = StaffB{...}>>}}

I don't know in lilypond 1.5.59 or 1.5.60.
-- 
Marco