An additive masterbatch composition comprising a semi-crystalline polyolefin carrier resin and an additive package comprising a product of a reaction of an acidic condensation catalyst and a secondary diarylamine. A moisture-curable polyolefin composition comprising the additive masterbatch composition and a (hydrolyzable silyl group)-functional polyolefin prepolymer. A method of making the compositions; a moisture-cured polyolefin composition prepared therefrom; a manufactured article comprising or made from the formulation; and a method of using the manufactured article.