Process for the preparation of a composition comprising a heterophasic propylene copolymer and talc, wherein the heterophasic propylene copolymer consists of (a) a propylene-based matrix wherein the propylene-based matrix consists of a propylene homopolymer and/or a propylene- α-olefin copolymer consisting of at least 70% by mass of propylene and up to 30% by mass of ethylene, based on the total mass of the propylene-based matrix wherein the propylene-based matrix is present in an amount of 60 to 95wt% based on the total heterophasic propylene copolymer and (b) a dispersed ethylene-α-olefin copolymer, wherein the dispersed ethylene-α-olefin copolymer is present in an amount of 40 to 5wt% based on the total heterophasic propylene copolymer and wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the heterophasic propylene copolymer is 100wt%, wherein the composition has a desired melt flow index in the range of 1 to 200dg/min as measured according to ISO1133 (2.16 kg/230°C), wherein at least part of the talc is surface-modified and wherein the amount of talc in the composition is from about 0.5 to at most 5wt% based on the heterophasic propylene copolymer, comprising the step of (a) melt-mixing the heterophasic propylene copolymer with the talc and a peroxide, wherein the amount of peroxide is chosen such that a composition comprising a heterophasic propylene copolymer and talc having the desired melt flow index is obtained, wherein the α-olefin in the propylene- α-olefin copolymer is selected from the group of α-olefins having 2 or 4-10 carbon atoms, wherein the amount of ethylene in the ethylene-α-olefin copolymer is in the range of 20-65wt% based on the ethylene-α-olefin copolymer and wherein the α-olefin in the ethylene-α-olefin copolymer is chosen from the group of α-olefins having 3 to 8 carbon atoms and any mixtures thereof, wherein at least 80 wt% of the talc in the composition is surface modified and wherein the surface-modified talc is a talc that is surface-modified with a polar substance selected from the group of glycols, silanes and amines. (a) a propylene-based matrix wherein the propylene-based matrix consists of a propylene homopolymer and/or a propylene- α-olefin copolymer consisting of at least 70% by mass of propylene and up to 30% by mass of ethylene, based on the total mass of the propylene-based matrix wherein the propylene-based matrix is present in an amount of 60 to 95wt% based on the total heterophasic propylene copolymer and (b) a dispersed ethylene-α-olefin copolymer, wherein the dispersed ethylene-α-olefin copolymer is present in an amount of 40 to 5wt% based on the total heterophasic propylene copolymer and wherein the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-α-olefin copolymer in the heterophasic propylene copolymer is 100wt%, wherein the composition has a desired melt flow index in the range of 1 to 200dg/min as measured according to ISO1133 (2.16 kg/230°C), wherein at least part of the talc is surface-modified and wherein the amount of talc in the composition is from about 0.5 to at most 5wt% based on the heterophasic propylene copolymer, (a) melt-mixing the heterophasic propylene copolymer with the talc and a peroxide, wherein the amount of peroxide is chosen such that a composition comprising a heterophasic propylene copolymer and talc having the desired melt flow index is obtained, wherein the α-olefin in the propylene- α-olefin copolymer is selected from the group of α-olefins having 2 or 4-10 carbon atoms, wherein the amount of ethylene in the ethylene-α-olefin copolymer is in the range of 20-65wt% based on the ethylene-α-olefin copolymer and wherein the α-olefin in the ethylene-α-olefin copolymer is chosen from the group of α-olefins having 3 to 8 carbon atoms and any mixtures thereof, wherein at least 80 wt% of the talc in the composition is surface modified and wherein the surface-modified talc is a talc that is surface-modified with a polar substance selected from the group of glycols, silanes and amines.