subwoofer in corner under shelf: reflection probs?

Just a question about whether having something above a subwoofer in a corner will create problems. I have a sealed inclosure sub (Velodyne DD12) that I have used successfully in a corner placement. I now want to put a shelf above it, and I'm wondering if that is going to cause problems with unwanted bass reflections etc. or otherwise compromise the sound?

thanks!

--dan