A detergent contains as a grayness inhibitor in the wash and aftertreatment of textile material containing synthetic fibers a graft polymer obtainable by grafting(a) a polyalkylene oxide which has a number average molecular weight of from 300 to 100,000 and is based on ethylene oxide, propylene oxide and/or butylene oxide with(b) N-vinlypyrrolidone and(c) a vinyl ester derived from a saturated monocarboxylic acid containing from 1 to 6 carbon atoms and/or a methyl or ethyl ester of acrylic or methacrylic acid in a weight ratio (a):(b):(c) of from 1:0.3:1 to 1:5:30, the order of the addition of (b) and (c) in the graft copolymerization being immaterial and it being possible for up to 1 mole % of the grafted-on monomers (c) to be hydrolyzed.