Lyrics vertically misplaced using instrument name

[Robert Schröter]

> I'm not top posting.

In the example below the lyrics to the first staff appear below the second, 
but are still correctly aligned horizontally. If you remove the instrument 
name of the first staff, the problem disappears, and the lyrics appear 
between the two staves.

A workaround is using a name to the first staff and then \Lyrics \with 
{alignBelowContext=...}

Regards, Robert

------------------

\version "2.10.33"
<<
  \new Staff { \set Staff.instrumentName = "Voice 1"
               { c'4 c' }
               \addlyrics { bla bla }
             }
  \new Staff { c'8 c' c' c' }
>>