Specialized Roubaix Seat Post Rubber Seal Loose

On my Specialized Roubaix Comp, the rubber seal where the seat post enters the frame works loose and slides up the seat post a little. The seat post itself is not loose and stays put, the issue is just with the seal. I not sure if the seal serves a functional purpose (i.e. to prevent water ingress) or if it is just for aerodynamics and appearance. However, it bothers me that will not stay put. How do I get it to stay put?