A method for controlling an internal combustion engine is disclosed. The method may include receiving knock data corresponding to knock levels over a time period. The method may also include determining from the knock data whether the knock levels change over the time period. Further, the method may include determining that a variation in the gas composition of the gaseous fuel supplied to the internal combustion engine has occurred when the knock levels change over the time period. In addition, the method may include adjusting an operating condition of the internal combustion engine to adapt a knock susceptibility of the internal combustion engine to the varying gas composition.