A burner for a gas turbine, having a combustion chamber, a first injector adapted to inject a first fuel into the combustion chamber and a second injector adapted to inject a second fuel being less reactive than the first fuel into the combustion chamber, wherein the burner is adapted to premix the fuels with an air flow before the fuel enter the reaction zone of the combustion chamber such that a first fuel flow of the first fuel has a first premixing stream line and a second fuel flow of the second fuel has a second premixing stream line, wherein each of the premixing stream lines begins with the beginning of the premixing with the air flow and ends at the location where the fuel enters the reaction zone and the length of the second premixing stream line is longer than the length of the first premixing stream line.