Abstract: The invention relates to a process of coating a substrate with a non-aqueous coating composition comprising a) a polyol, b) a polyisocyanate crosslinker, c) a metal based catalyst for the addition reaction of hydroxyl groups and isocyanate groups, d) a thiol-functional compound at least partly deactivating the metal based catalyst, and e) a photolatent base which can be activated by actinic radiation, wherein the photolatent base prior to activation has a pKa value below 8, and wherein at least 60 mol-% of all isocyanate-reactive groups are hydroxyl groups, comprising the steps of: i) applying the coating composition to a substrate and ii) curing the coating composition.