src/Tools/jEdit/src/document_model.scala

 
   @tailrec final def await_stable_snapshot(): Document.Snapshot =
   {
     val snapshot = this.snapshot()
     if (snapshot.is_outdated) {
-      PIDE.options.seconds("editor_output_delay").sleep
+      PIDE.options.seconds("editor_output_delay").sleep()
       await_stable_snapshot()
     }
     else snapshot
   }
 }