Matlab offset-contour plot with labels

Apteronotus

I want to have a labeled contour plot, plotted on the horizontal plane z=3.
The closest I've come is the following

[C,h] = contour(X,Y,Z);

hh = get(h,'Children');

for i=1:numel(hh)
set(hh(i), 'ZData',3*ones(size(X)));
clabel(C,hh)
end

The problem is that I get two sets of labels. The first is plotted on the offset contour lines, but the second is plotted on the horizontal plane z=0!!

Any suggestions?