Vias between top and bottom ground planes

Hi all, it is sometimes desirable to put some closely spaced vias between the ground planes on the top and bottom to reduce the impedance at very high frequencies.

I have tried several different ways with out success. Eagle keeps putting a space around the via so that it does not make an electrical connection. Does anyone know how to do this? Thanks, Ed.

You need to assign the ground plane net name to the vias.