A capacitor assembly that is capable of exhibiting good electrical properties even under a variety of conditions is provided. More particularly, the capacitor assembly includes a capacitor element, which comprises a porous anode body that contains a valve metal compound, a dielectric that overlies the anode body and includes an oxide of the valve metal compound, and a solid electrolyte that overlies the dielectric. The solid electrolyte includes a conductive polymer and a hydroxy-functional polymer. Further, the capacitor element comprises an organofunctional silane compound that is bonded to the oxide of the dielectric and is capable of bonding to the hydroxy-functional polymer.