figuredBassAlterationDirection don't work in contexts

[Klaus Rettinghaus]

% figuredBassAlterationDirection rule
% isn't working when using with a
% context staff
\version "2.18.2"

<<
 \new Staff = "myStaff"
 \figuremode {
   \set figuredBassAlterationDirection = #RIGHT
   <4+>4 <10 6->8 s8
   \bassFigureStaffAlignmentDown
   <6 4>4 <6- 4>
 }
 %% Put notes on same Staff as figures
 \context Staff = "myStaff"
 {
   \clef bass
   c4 c'8 r8 c4 c'
 }
>>