Ending operation of dual fuel engine in gaseous fuel mode

A method for controlling operation of a dual fuel internal combustion engine is disclosed. The method comprises initiating an ending process of a gaseous fuel mode by stopping supply of gaseous fuel. During the ending process, combusting remaining gaseous fuel together with liquid fuel in a subgroup (12) of cylinders (8, 9, 10, 11). The method further comprises determining that the difference of a combustion process parameter in at least one cylinder (11) of the subgroup (12) and at least one cylinder (8, 9, 10) not in the subgroup (12),which combusts liquid fuel only, is within a preset acceptable range, and indicating that the ending process is completed.