The present invention relates to a polyolefin composition comprising (A) a polyolefin, (B) a benzil derivative comprising, preferably consisting of, the structural unit according to the following formula (I) wherein R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 independently from each other are hydrogen, or a hydrocarbyl group which may contain heteroatoms or at least two of said R1, R2, R3, R4, R5, R6, R7, R8, R9 and R10 together with the ring atoms of the ring system of formula (I) they are attached to, form a further aromatic or non-aromatic ring fused to the ring system of formula (I) and at least R1 or R2 is an ester group. The invention also relates to a wire or cable, in particular a medium, high or extra high voltage cable, comprising such a composition, and to the use of such a composition for the production of a wire or cable, in particular a medium, high or extra high voltage cable.