A composition for an insulating layer of an electric cable is described. The composition contains an ethylene plastic as the base resin and further contains up to about 5 % by weight of additives including antioxidant, and peroxide cross-linking agent. The composition is characterised in that the antioxidant additive includes a compound of the formula (V): R1(-(C=O)O-)k(CH2)1-S-(CH2)m(-O-(C=O)-)nR2 where R1 and R2, which are the same of different, are C7-C23 alkyl, C7-C23 alkenyl, R3-Ar-, Ar-R3-, or AR-, where R3 is C8-C24 alkyl and Ar is C6-C14 aryl; k and n, which are the same of different, are 0 or 1, 1 and m, which are the same or different, are integers ≥0; with the proviso that the compound is free from phenolic groups; and that the compositions is free from compounds having the formula (VI): R-O-(C=O)-CH2CH2SCH2CH2-(C=O)-O-R where R is a C8-C20 alkyl group.