The invention therefore relates to a process for preparation of SiOC-linked, linear (AB)d polydimethylsiloxane-polyoxyalkylene block copolymers of the general formula [(R2SiO)x(CnH2nO)y]d, in which R are monovalent C1-C18, preferably C1-C4, hydrocarbon radicals, n is a number from 2 to 4, preferably 2 or 3, x ≧5, y ≧10, d ≧3, via reaction of aminosiloxanes having primary amino groups with polyoxyalkylenediols, which comprises concomitant use of one or more tertiary amines as catalyst.