Rubber composition intended for the manufacture of tire casings which have improved hysteretic properties and scorch safety, based on at least one elastomer and silica by way of reinforcing filler enclosing a reinforcing additive consisting of the mixture and/or the product of in situ reaction of at least one functionalized polyorganosiloxane compound containing, per molecule, at least one functional siloxy unit capable of bonding chemically and/or physically to the surface hydroxyl sites of the silica particles and at least one functionalized organosilane compound containing, per molecule, at least one functional group capable of bonding chemically and/or physically to the polyorganosiloxane and/or the hydroxyl sites of the silica particles and at least one other functional group capable of bonding chemically and/or physically to the polymer chains.