Abstract: The invention relates to an additive suitable for increasing compressive strength during the production of polyurethane soft foam, which contains at least one compound (V) containing, (i) more than three hydrogen atoms which are reactive with respect to isocyanates, (ii) an average hydroxyl number, determined according to DIN 53240-1: 2013-06, from 110-280 mg KOH/g, preferably 120-250 mg KOH/g, and (iv) >50 wt.-% ethylene oxide bound in the molecule, wt.-% with respect to the total alkylene oxide, and to a method for producing polyurethane foams and to a polyurethane foam and to the use thereof as described.