src/Pure/PIDE/session.ML

       (Thy_Info.get_names ()) Keyword.empty_keywords;
   session_finished := true);
 
 fun save heap =
  (Execution.shutdown ();
-  Future.shutdown ();
   Event_Timer.shutdown ();
   Future.shutdown ();
   ML_System.share_common_data ();
   ML_System.save_state heap);