1. A method for controlling an internal combustion engine operating on at least partly gaseous fuel, the method comprising: providing a desired burn rate profile corresponding to a desired operation of the internal combustion engine; selecting a set of operating parameters such that an operation of the internal combustion engine with a first gas composition produces a first burn rate profile that corresponds to the desired burn rate profile; operating the internal combustion engine with the set of operating parameters using a second gas composition; receiving pressure data corresponding to a cylinder pressure profile; deriving from the pressure data a 2nd burn rate profile; and deriving at least one of a relative burn rate profile and a cumulative burn rate profile for each combustion event, the cumulative burn rate profile being an accumulated relative burn rate profile over the duration of one combustion cycle determining the second burn rate profile differs from the desired burn rate profile thereby indicating that the second gas composition differs from the first gas composition; adjusting an ignition timing from among the set of operating parameters of the internal combustion engine to approach the desired burn rate profile.