The invention relates to a method of making a polymer-modified polyol having a solid content from 13 to 55 wt. % wherein an olamine is reacted with an organic polyisocyanate in the presence of a base polyol and at least one catalyst, wherein said at least one catalyst is a zinc carboxylate, and wherein the base polyol has hydroxyl functions wherein more than 20% of said hydroxyl functions are primary hydroxyl functions. The invention further relates to a polymer-modified polyol obtainable with the method of the invention, the use of the polymer-modified polyol for the preparation of optionally foamed plastics, and to a method for the preparation of optionally foamed plastics using the polymer-modified polyol of the invention.