The present invention relates to a capacitor comprising i) an electrode body comprising an electrode material, wherein a dielectric layer comprising a dielectric material at least partially covers a surface of the electrode body; ii) a solid electrolyte layer comprising a solid electrolyte material that at least partially covers a surface of the dielectric layer, wherein the solid electrolyte material comprises a conductive polymer; iii) an anode contact that is in contact with the electrode body and that comprises copper, metal-plated copper or a copper-containing alloy; and iv) a cathode contact that is in contact with the solid electrolyte layer; wherein the capacitor further comprises at least one metal ion migration inhibitor. The present invention also relates to a process for the production of a capacitor, to a capacitor obtainable by such a process, to electronic circuit comprising the capacitor according to present invention and to the use of these capacitors in electronic circuits.