No output mix meter display when direct monitoring

Am I missing something. If I dont have direct monitoriing turned on, the output mix meter works fine. When I turn direct monitoring on, the output meter stops displaying the output level. Does anyone know how to get it to display with direct monitoring on? Seems really weird to me. I want to use this at a gig with 2 mixes for the foldback. How can I tell if the band are hearing the sound (apart from the waving I guess!)? I certainly wont be able to hear their mix from the mixing position?