src/Pure/Concurrent/timeout.ML

       val self = Thread.self ();
       val start = Time.now ();
 
       val request =
         Event_Timer.request {physical = false} (start + timeout)
-          (fn () => Standard_Thread.interrupt_unsynchronized self);
+          (fn () => Isabelle_Thread.interrupt_unsynchronized self);
       val result =
         Exn.capture (fn () => Thread_Attributes.with_attributes orig_atts (fn _ => f x)) ();
 
       val stop = Time.now ();
       val was_timeout = not (Event_Timer.cancel request);