Oligo(β-amino ester)s, obtainable by aza-Michael addition of S-substituted primary aminothiols to oligoesters of monoethylenically unsaturated monocarboxylic acids and bivalent, trivalent or tetravalent alcohols, are included in surfactant-containing aqueous detergent solutions in order to prevent the transfer of textile dyes from colored textiles to uncolored textiles or textiles of other colors when washing textiles together in the detergent solutions.