help, my bunny keeps digging hay out into his litter box :/

his hay is stored in a box with an opening at the bottom and his litter box is right under it so that he can eat and poop at the same time. he really likes digging out the hay and it becomes soiled. so much is wasted and it gets everywhere!

i know it's common for rabbits to dig and pick at their hay, but are there any methods to reduce this issue? how do you contain the mess?