Polyisocyanates which have 1,2,4,-triazole-blocked isocyanate groups and a blocked isocyanate group content of 7 to 14 wt. % and which are reaction products of A) a polyisocyanate component selected from (i) lacquer polyisocyanates based on (cyclo)aliphatic diisocyanates or (ii) mixtures of these lacquer polyisocyanates with cycloaliphatic diisocyanates of a maximum molecular weight of 300, B) 50 to 80 equivalent-%, based on the isocyanate groups of component A), of a monofunctional isocyanate group blocking agent containing at least 90 wt. % of 1,2,4-triazole, C) 10 to 30 equivalent-%, based on the isocyanate groups of component A), of a polyester component having an OH number of 56 to 250 and D) 0 to 20 equivalent-%, based on the isocyanate groups of component A), of selected hydrazine derivatives. The present invention is also directed to the use of these blocked polyisocyanates as crosslinking agents in one-component polyurethane stoving lacquers.