The present invention relates to a process for the manufacture of a long glass fibre reinforced polypropylene composition at a line speed of at least 6.7 m/s comprising the steps of a) providing at least one continuous glass multifibre strand, b) applying from 0.5 to 20 wt. % based on the weight of the composition of an impregnating agent to said at least one continuous multifibre strand, c) applying a sheath of a polypropylene composition around the strand obtained in step b) so as to form a sheathed continuous multifibre strand, wherein the impregnating agent contains at least 90 wt. % of microcrystalline wax based on the weight of the impregnating agent.