Fitting Kitchen Sink without gasket

Hi all,

I purchased a Franke Titan 1.5 bowl sink a few weeks ago from ToolStation.

I'm supposed to be fitting it in the kitchen this weekend. Have just read the (very brief) installation guide and it says (and I don't have the notes to hand so working from memory here) something to the effect of "seal in with a big bead of silicone or use the supplied rubber seal".

Slight problem. Just checked the box and it seems that the rubber seal is missing.

The notes imply that it is OK to fit...

Fitting Kitchen Sink without gasket