Anti-aliasing problem with vector shapes in AE

Hi!

I have encountered a problem with using vector shapes tilted at 45 degree angle.

I have built a grid of boxes tilted in a 45 degree angle and imported them as into AE by copy&paste the shapes on a adjustment layer (making the shapes masks).

The problem is that I can see through the sides of the boxes. Even though they are pixel perfect alianed to eachother. I think it has to do with with the antialiasing.

I have tryed to "expaned" the masks but then I only subtract drom the other masks.

Any ideas?

Thanks!