Mk1 Tailgate lock plastic seal fitting help please.......

Hi I'm trying  to fit a new tailgate lock seal on my mk1 golf but not doing very well.  Small plastic ring.  

Any one else done this?  Or have any advice on how best to fit.  

It seems the seal has a very small ridge and seems to push out of the hole when I try and put the lock through.  
I'm not sure if I've even got it the right way round. :/ If anyone has some knowledge or experience on fitting this little part I would be most grateful.  

Cheers Mike 

I did it last year on my cabby but don't remember any probs😁

Sorry