An image forming apparatus, and a method of controlling it. The apparatus performs, in a case where at least one function out of a plurality of functions of the apparatus ceases to be usable, degeneracy control for operating to provide functions other than the at least one function, and stores information indicating a degeneracy control state is entered. The apparatus controls so as to activate without initialization operation of an image forming mechanism in a case where it is determined that the activation is due to the return from a power saving mode and the information is stored and so as to activate with the initialization operation when the activation is due to a power of the apparatus being turned on.