Bug Plotting Heaviside Step Function

I'd expect this:

fplot(@(t) (heaviside(t) - heaviside(t-1)), [-5 5]);

to show 1 between [0,1) and 0 elsewhere. Instead, I get a flat line of all zero. If I change the plot range:

fplot(@(t) (heaviside(t) - heaviside(t-1)), [-2 2]);

that creates the plot that I'd expect over that range.

Further exploration shows that this works:

fplot(@(t) (heaviside(t) - heaviside(t-1)), [-3 3.25]);

but this one does not:

fplot(@(t) (heaviside(t) - heaviside(t-1)), [-3 3.3]);

This looks like a bug in Matlab. Any ideas?