A reduction is prevented in stacking efficiency of a sheet stacking apparatus due to a wrong setting of a stacking tray performed by a user thereby achieving a high stacking efficiency. In a control method for controlling an image forming apparatus including a sheet stacking control unit configured to stack sheets, subjected to printing in a print job, on one of a plurality of removable sheet stacking units, the control method includes specifying a sheet discharging unit used in the print job, determining whether a sheet stacking unit corresponding to the specified sheet discharging unit is properly set, and, in a case where it is determined that the sheet stacking unit is not properly set, restricting conveying sheets to the sheet stacking unit.