How can I stop my Chickens from pooping in their nest boxes?

[BongeDundee]

My new flock has just started laying eggs, and I'm so proud because they are laying them inside their next box, but its also where they do their business. Is there any way I can encourage them to not poop in their next boxes?
Thanks.

 

[BantamLover21]

Do you think your chickens are fouling the nest box while they're laying an egg, or are they able to roost over the nest boxes at night? I can't think of a good solution to the former problem (other than changing bedding regularly), but the second problem could be avoided by changing the nest box design and/or moving roosts.

 

[aart]

Wonders if they have been roosting(sleeping) in the nests?
They poop a lot during the night and so should not be allowed to sleep in the nests.
Roosts should be about a foot higher than the nests because they like to roost as high as possible.