Printing system, method of controlling printing system, and non-transitory computer-readable storage medium

A printing system comprising:

• a printing unit configured to print an image on a sheet;
• a sheet processing unit configured to perform a designated sheet process for the printed sheet using a single die for performing the designated sheet process out of a plurality of dies for performing sheet processes different from each other, wherein the single die for performing the designated sheet process is manually selected from the plurality of dies by a user and is manually attached to the sheet processing unit;
• and
• a control unit configured to control the printing unit,
• wherein, in a case where the single die for performing the designated sheet process is not attached to the sheet processing unit, it is determined, before the printing unit starts printing the image on a first sheet on which the printing unit prints the image firstly among sheets on which the designated sheet process is to be performed, not to perform the designated sheet process for the sheets on which the designated sheet process is to be performed, and the printing unit starts printing the image on the sheets on which the designated sheet process is to be performed after the determination.