[Maxima] Bug in Gosper (simpler version)? (was: Symbolic summation)

[Michel Van den Bergh]

(%i1) display2d:false;

(%o1) false
(%i2) load(zeilberger);

(%o2)
?\/usr\/share\/maxima\/5\.11\.0\/share\/contrib\/Zeilberger\/zeilberger\.mac
(%i3) AntiDifference(-(1/(n+1)-1/n),n);

(%o3) (-n-1)*(1/n-1/(n+1))
(%i4) AntiDifference((1/(n+1)-1/n),n);

Unknown operator :  -
1/(n+1)-1/n  is not hypergeometric in  n
(%o4) NON_HYPERGEOMETRIC

Regards,
Michel