The present invention relates to a stabilized monomer composition comprising at least 50 wt.-%, based on the total weight of the stabilized monomer composition, of a thiophene derivative monomer having the general formula (I) in which R1 and R2 stand, independently of one another, for hydrogen, for an optionally substituted C1-C20-alkyl group or C1-C20-oxyalkyl group, optionally interrupted by 1 to 5 oxygen atoms and/or sulfur atoms, or jointly for an optionally substituted C1-C20-dioxyalkylene group or C6-C20-dioxyarylene group, and 0.001 to 10 wt.-%, based on the total weight of the stabilized monomer composition, of a stabilizer. The present invention also relates to a method for the manufacture of a capacitor, a capacitor obtained by this method, the use of a stabilized monomer composition and to the use of a stabilizer.