An electrolytic capacitor is provided having an inner case housing a capacitor element and an electrolyte, which is sealed by an inner cap insulated from the body of the inner case by a gasket, with the anode terminal of the capacitor element connected to the inside face of the inner cap and an anode lead connected to the outside face of the inner cap. The inner case is placed in an outer case having a sleeve surrounding the body of the inner case and an outer cap with a hermetic seal overlaying the inner cap. An insulating spacer is positioned between the inner cap and the outer cap, whereby the spacer resists movement of the inner cap, thereby preventing outward expansion of the inner case, which otherwise might lead to failure, especially at relatively high operating temperatures.