Printing to CUPS printer instances does not work

When trying to print to a so-called CUPS printer instance, no print job is triggered.

Assuming, a CUPS printer "myprinter" is set up on the system, the problem can be reproduced as follows:

• create a CUPS printer instance "myinstance" of the printer with any option set to a specific value, e.g. by running the following command: 'lpoptions -p myprinter/myinstance -o foo=bar'
• open any application that uses the Qt print dialog (e.g. Kate)
• Open print dialog, e.g. by pressing Ctrl+P
• select the printer instance created previously ("myprinter/myinstance")
• click "Print" to start the print job

Result: Nothing happens. No print job is created.

Expected result: A print job should be created and the document should be printed.