Question: evaluation of expression using int vs Int

Can anyone explain why I get a different answer if I use int instead of Int in the following evaluation:

> evalf(subs(r = 1, Int(Int(Dirac(x1+x2-r)*q, x1 = 0 .. 1), x2 = 0 .. 1)));
1.676209155
> evalf(subs(r = 1, int(int(Dirac(x1+x2-r)*q, x1 = 0 .. 1), x2 = 0 .. 1)));
0.
The first answer with Int seems correct to me, but maybe there is some hidden assumption that I'm not seeing. 
Can anyone help?
Thanks,
Francois
B.T.W. I'm using Maple 11, in case its a bug and not a feature!
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