src/Pure/ProofGeneral/proof_general_emacs.ML

           ProofGeneralPgip.init_pgip_channel (! Output.priority_fn);
           setup_thy_loader ();
           setup_present_hook ();
           set initialized);
         sync_thy_loader ();
-       change print_mode (cons proof_generalN o remove (op =) proof_generalN);
+       change print_mode (update (op =) proof_generalN);
        Isar.sync_main ());
 
 end;