An acidic aqueous composition for electrolytically depositing a copper deposit, the composition comprising (i) copper (II) ions, (ii) one or more than one compound of formula (Ia) wherein each independently - R 4 and R 5 are selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C5 alkyl, branched C3 to C5 alkyl and a moiety of formula (lb) - R 1 , R 2 , R 3 , and R 6 are selected from the group consisting of hydrogen, methyl and ethyl, - A 1 , A 2 and A 3 are selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C12 alkyl, branched C3 to C12 alkyl, unsubstituted quinoline, substituted quinoline, unsubstituted isoquinoline, and substituted isoquinoline, wherein said substituted quinoline and substituted isoquinoline are independently substituted with one, two, three or more than three substituents, each substituent being independently selected from the group consisting of halogen, alkyl, nitro, sulfonate, and alkoxy, - s is 0 or 1, - n is 1, 2 or 3, - o, p, q, and t are integers in the range from 0 to 100, with the proviso that - at least one of A 1 , A 2 and A 3 is independently one of said substituted quinoline or said substituted isoquinoline, and - independently o + p + q + t = 5 to 100, (iii) one, two, three or more than three further compounds, which are different from the compound of formula (la), and wherein the composition does not contain tin ions. (i) copper (II) ions, (ii) one or more than one compound of formula (Ia) wherein each independently - R 4 and R 5 are selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C5 alkyl, branched C3 to C5 alkyl and a moiety of formula (lb) - R 1 , R 2 , R 3 , and R 6 are selected from the group consisting of hydrogen, methyl and ethyl, - A 1 , A 2 and A 3 are selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C12 alkyl, branched C3 to C12 alkyl, unsubstituted quinoline, substituted quinoline, unsubstituted isoquinoline, and substituted isoquinoline, wherein said substituted quinoline and substituted isoquinoline are independently substituted with one, two, three or more than three substituents, each substituent being independently selected from the group consisting of halogen, alkyl, nitro, sulfonate, and alkoxy, - s is 0 or 1, - n is 1, 2 or 3, - o, p, q, and t are integers in the range from 0 to 100, with the proviso that - at least one of A 1 , A 2 and A 3 is independently one of said substituted quinoline or said substituted isoquinoline, and - independently o + p + q + t = 5 to 100, - R 4 and R 5 are selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C5 alkyl, branched C3 to C5 alkyl and a moiety of formula (lb) - R 1 , R 2 , R 3 , and R 6 are selected from the group consisting of hydrogen, methyl and ethyl, - A 1 , A 2 and A 3 are selected from the group consisting of hydrogen, methyl, ethyl, linear C3 to C12 alkyl, branched C3 to C12 alkyl, unsubstituted quinoline, substituted quinoline, unsubstituted isoquinoline, and substituted isoquinoline, wherein said substituted quinoline and substituted isoquinoline are independently substituted with one, two, three or more than three substituents, each substituent being independently selected from the group consisting of halogen, alkyl, nitro, sulfonate, and alkoxy, - s is 0 or 1, - n is 1, 2 or 3, - o, p, q, and t are integers in the range from 0 to 100, - at least one of A 1 , A 2 and A 3 is independently one of said substituted quinoline or said substituted isoquinoline, and - independently o + p + q + t = 5 to 100, (iii) one, two, three or more than three further compounds, which are different from the compound of formula (la), and <EOS>