A composition comprising a source of metal ions and at least one additive comprising a polyalkyleneimine backbone, said polyalkyleneimine backbone having a molecular weight Mw of from 300 g/mol to 1000000 g/mol, wherein the N hydrogen atoms in the backbone are substituted by a polyoxyalkylene radical and wherein the average number of oxyalkylene units in said polyoxyalkylene radical is from 1.5 to 10 per N—H unit.