Lighting with persistant levels and sub-levels?

I have a persistent level with 2 sub-levels. One sub-level has the landscape and all the dynamically lit objects and the second sub-level has the static lighting objects. I build the sub-level’s lighting separately. Unfortunately, when I open the top level, I get the lighting needs to be rebuilt warning message. It seems it wants to rebuild the landscape with static lighting even though the sub-level the landscape belongs to is dynamic. Is there a way around this?