Beast will not bake terrain lightmaps above 1024x

I am lightmapping a terrain, and I want to have the lightmap size be 4096x, but even if I set it to the max size it just looks like 1024x. At the bottom of the lightmapping window, there is an indication that there is only a 1024x lightmap. How can I get Beast to bake a 4096x lightmap for my terrain?

Thanks for any help.