Roof Rain Channel Trim

[Blobcat]

Whilst washing the salt off my E320cdi today. I noticed (again) that the trim in the rain channel in the roof has popped up. It normally does this in the summer with a bit of heat on it. I just press it back down again but the white plastic clip doesn't seem to be doing its job.
Any long term solutions? I'm not really keen on using glue on it.

 

[television]

A little impact adhesive will do no harm,and not effect the paint, it can be wiped off with petrol or lighter fluid.

Malcolm