A heterophasic copolymer composition obtained by a process comprising polymerising in multiple steps and multiple polymerisation reactors propylene monomer and a comonomer selected from ethylene, alpha-olefins having 4 to 10 carbon atoms and their mixtures, in the presence of an olefin polymerisation catalyst comprising a solid catalyst component and a co-catalyst, wherein the solid catalyst component comprises titanium, magnesium, halogen and an internal donor of the formula (I):




wherein R1 and R2 are the same or different being a linear or branched C1-C12-alkyl group and R is hydrogen or a linear, branched or cyclic C1 to C12-alkyl.