#'extra-offset not working

[David Bobroff]

I'm having a weird problem.  In the following example I'm able to move a 
rehearsal mark but not a \markup.  Am I missing something or is this 
some sort of bug?

-David

%%***** BEGIN LILYPOND *****

\version "2.11.40"

\score {
        \relative c {
        \set Score.skipBars = ##t
        \once \override Score.TextScript #'extra-offset = #'(0 . 4)     
        R1*4^\markup{"some text taking up space"}
        \once \override Score.RehearsalMark #'extra-offset = #'(0 . -4)
        \mark \default
        R1*4
        }
}

\paper {
        ragged-right = ##t
}


%%***** END LILYPOND *****