src/Pure/Concurrent/event_timer.ML

   then manager_loop () else ();
 
 fun manager_check manager =
   if is_some manager andalso Thread.isActive (the manager) then manager
   else
-    SOME (Standard_Thread.fork {name = "event_timer", stack_limit = NONE, interrupts = false}
+    SOME (Isabelle_Thread.fork {name = "event_timer", stack_limit = NONE, interrupts = false}
       manager_loop);
 
 fun shutdown () =
   Thread_Attributes.uninterruptible (fn restore_attributes => fn () =>
     if Synchronized.change_result state (fn st as State {requests, manager, ...} =>