The present invention relates to hydroxyaldimines of formula (I), to their reaction products, in particular products of their reaction with polyisocyanates, and to compositions comprising isocyanate groups and containing such reaction products. The hydroxyaldimine permits compositions which have good storage stability, a long open time, low odour, rapid, bubble-free curing and good mechanical properties, and which are not susceptible to plasticizer migration and have a particularly low content of monomeric diisocyanates. In particular, it permits reactive hot-melt adhesives with a particularlygood workability.