Reduction clearing of polyester textiles

A process for reduction clearing dyed or printed polyester textiles comprises adding, to the acidic dyeing liquor or the wash bath, an aftertreatment composition comprising as components a) at least one compound of the formula (I): Am[(CR1R2)mSO2M]p,q, where A is NR33-q or OR42-p, R1, R2, R4 are each hydrogen or C1-C6-Alkyl, R3 represents identical or different radicals selected from the group consisting of hydrogen, C1-C20-alkyl, C3-C8-cycloalkyl opt. substituted by from one to three C1-C4-alkyl radicals, M is the equivalent of an ammonium, alkali metal or alkaline earth metal ion, m is 0 or 1, p is 1 or 2, q is 1, 2 or 3 subject to the provisos that at least one of R1, R2, R4 is C1-C6-alkyl when A is OR42-p and that, if m is 0: p, q are each 2 and the compound of the formula (I) is used together with sufficient acid acceptor to raise the pH of the dyeing liquor or of the wash bath by from 1 to 3 units, (b) optionally at least one compound of the formula (II): A[(CR1R2)SO3M]p,q, where A, R1, R2, R3, R4, M, p and q are each as defined for the formula (I), (c) and optionally further additives.