The invention relates to a coating system comprising a binder composition comprising a polymer having a Mn of 6,000 to 60,000 g/mol, a Mw of 20,000 to 300,000 g/mol, a Tg of 30 to 180° C. and an acid value of at most 3.0 mg KOH/g, and a RMA crosslinkable coating composition comprising a component A with at least two acidic protons C—H in activated methylene or methine groups, a component B with at least two activated unsaturated C═C groups and a base crosslinking catalyst C; and its use for improving adhesion of the RMA crosslinkable coating composition, in particular to wood substrates.