Bus error when attaching voice context to grouping

[Douglas Ligertwood]

% This fails with a bus error.
% I'm uncertain if this should be valid code,
% but a clearer error message would be helpful.

\version "2.18.2"

\layout {
        \context {
                \Voice
                \name trebleVoice
                \alias Voice
        }
        \context {
                \ChoirStaff
                \accepts trebleVoice
        }
}

\new trebleVoice { a1 }