The present invention relates to a polypropylene composition comprising (A) a copolymer of propylene and comonomer units selected from ethylene and alpha-olefins having from 4 to 12 carbon atoms with a total amount of comonomer units of from 10.0 to 16.0 wt %, based on the total amount of monomer units in the polypropylene composition, and (B) an alpha-nucleating agent; wherein the polypropylene composition has a xylene cold soluble (XCS) fraction in a total amount of from 25.0 to 50.0 wt %, based on the total weight amount of the polypropylene composition, with an amount of comonomer units of at least 23.0 wt %, based on the total amount of monomer units in the xylene cold soluble (XCS) fraction, a melt flow rate MFR2 of from 0.5 to 5.0 g/10 min, and a flexural modulus of not more than 470 MPa, an article comprising said polypropylene composition, preferably a cable comprising an insulation layer comprising said polypropylene composition and the use of said polypropylene composition as cable insulation for medium and high voltage cables.