Any decent ways of adding weight to a hollow wooden door?

As per title. The problem I have with the door is that its so light that I cant swing the door shut as room air pressure stops it just before it closes. I'm currently changing a bedroom door knob for a privacy door knob so can see inside the door from where the door latch would normally be and it looks like its filled mostly with polystyrene foam. Forgive the potato quality picture, its all I could get by holding my phones camera at the latch hole whilst holding a torch in my mouth. :p

I'm going to guess that its unlikely I'll be able to do anything to the door to add more weight?

Submitted April 09, 2016 at 01:24AM by SirSpaffsalot http://ift.tt/1S84rGS