The present invention is directed to process for making a packaging, said packaging comprising a container (2) with a container body (5) and a container opening having an upper edge, said packaging further comprising a closure (4) for closing said container, the container and the closure being made out of polyethylene terephtalate (PET), polyethylene naphtalate (PEN), or a combination thereof, said container (2) and said closure (4) comprising respectively first (8) and second (9) attachment means, characterized in that: said process comprising the steps of in order: (i) fitting said first (8) and second (9) attachment means to each other, (ii) deforming at least one of the first and/or second attachment means up to the point of permanent deformation of the PET or PEN material, by punching, rolling, or a combination thereof, so as to create a permanent, leak-tight, attachment between said container and said closure.