An aqueous binder composition comprising a) a polymer P in the form of an aqueous multistage polymer dispersion of dispersed polymer particles, where the polymer particles comprise a first polymer having a glass transition temperature of at least 30°C and being made of ethylenically unsaturated monomers M-A, and a second polymer having a glass transition temperature of not more than 20°C and being made of ethylenically unsaturated monomers M-B, where the ethylenically unsaturated monomers M-A and M-B together comprise: i. 85% to 99.45% by weight, based on the total amount of monomers M-A + M-B, of at least one neutral, monoethylenically unsaturated monomer M1 having a solubility in water of at most 50 g/l at 25°C and 1 bar; ii. 0.5% to 10% by weight, based on the total amount of monomers M-A + M-B, of at least one neutral, monoethylenically unsaturated monomer M2 having a solubility in water of at least 100 g/l at 25°C and 1 bar; iii. 0.05 to 0.5% by weight, based on the total amount of monomers M-A + M-B, of one or more monoethylenically unsaturated monomers M3 having an acidic group; and iv. optionally from 0 to 5% by weight, based on the total amount of monomers M-A + M-B, of one or more monomers M4 having at least two non-conjugated ethylenically unsaturated double bonds; and b) at least one carbodiimide having at least two carbodiimide moieties, which are bound to an aliphatic carbon atom. a) a polymer P in the form of an aqueous multistage polymer dispersion of dispersed polymer particles, where the polymer particles comprise a first polymer having a glass transition temperature of at least 30°C and being made of ethylenically unsaturated monomers M-A, and a second polymer having a glass transition temperature of not more than 20°C and being made of ethylenically unsaturated monomers M-B, where the ethylenically unsaturated monomers M-A and M-B together comprise: i. 85% to 99.45% by weight, based on the total amount of monomers M-A + M-B, of at least one neutral, monoethylenically unsaturated monomer M1 having a solubility in water of at most 50 g/l at 25°C and 1 bar; ii. 0.5% to 10% by weight, based on the total amount of monomers M-A + M-B, of at least one neutral, monoethylenically unsaturated monomer M2 having a solubility in water of at least 100 g/l at 25°C and 1 bar; iii. 0.05 to 0.5% by weight, based on the total amount of monomers M-A + M-B, of one or more monoethylenically unsaturated monomers M3 having an acidic group; and iv. optionally from 0 to 5% by weight, based on the total amount of monomers M-A + M-B, of one or more monomers M4 having at least two non-conjugated ethylenically unsaturated double bonds; and i. 85% to 99.45% by weight, based on the total amount of monomers M-A + M-B, of at least one neutral, monoethylenically unsaturated monomer M1 having a solubility in water of at most 50 g/l at 25°C and 1 bar; ii. 0.5% to 10% by weight, based on the total amount of monomers M-A + M-B, of at least one neutral, monoethylenically unsaturated monomer M2 having a solubility in water of at least 100 g/l at 25°C and 1 bar; iii. 0.05 to 0.5% by weight, based on the total amount of monomers M-A + M-B, of one or more monoethylenically unsaturated monomers M3 having an acidic group; and iv. optionally from 0 to 5% by weight, based on the total amount of monomers M-A + M-B, of one or more monomers M4 having at least two non-conjugated ethylenically unsaturated double bonds; and b) at least one carbodiimide having at least two carbodiimide moieties, which are bound to an aliphatic carbon atom.