A composition comprising: (I) 55 to 95% by weight of an heterophasic polyolefin composition comprising 8 to 50% by weight of a crystalline propylene polymer fraction and 50 to 92% by weight of an elastomeric propylene fraction; (II) 2 to 20% by weight of an oxidized polyethylene wax having an acid number of 5 to 35 mg KOHIg, a molecular weight Mn of 1,000 to 100,000, and a melting point comprised between 92° C. and 140° C.; and (III) 3 to 25% by weight of a styrene block copolymer.