After setting SUID

-rwSrwxr-x 1 mike mike 0 Dec 5 11:24 freddy

if you see 'S' then it means that the file has no executable permissions for that user.

consider that if the file has executable permissions already and you are setting SUID

chmod u+s freddy

-rwsrwxr-x 1 mike mike 0 Dec 5 11:24 freddy

you should see a smaller 's' in the executable permission position.