Loft hatch opens with wind?

I have a loft hatch above the boiler in my room - which is not the main loft opening - and when it's a really windy night, the hatch flaps open and close which is understandably really quite scary. There is no way to get to that part of the loft through the main attic, so is there anything i can do to stop it opening? We tried sliding something on top of it, then pulling it back over but that hasn't seemed to work. Any suggestions? :)