The invention relates to a vulcanizable polymer composition comprising a) an polymer having an iodine value of lower than 400 g/100 g polymer, whereby the polymer is an elastomeric polymer that is a copolymer of ethylene, one or more C3 to C23 α-olefins and a polyene monomer, preferably a copolymer of ethylene, propylene and a polyene monomer are b) an organic peroxide having aromatic groups and c) a zeolite having a pore size of 3 to 6 Å.