what keeps the drive shaft attached to the gearbox on my renault megane(98)?

I have just replaced the O/S drive shaft on my renault megane and as the removal was very simple i assumed that the fitting of the new one would just be the reverse of this so that what i did, how ever the gearbox end of the drive shaft doesn't seem to have connected properly as i am able to pull it away from the gearbox thus leading me to believe that i haven't connected it properly. I pushed it on as hard as possible but i can still pull it away from the gearbox. is there supposed to some sort of retaining/ spring clip to hold the drive shaft to the gearbox? ASAP responce please as traveling away this saturday and really don't want it to come off or damage anything else. thank you. Calum :)