--- a/src/Pure/System/event_bus.scala Thu Feb 20 14:17:28 2014 +0100
+++ b/src/Pure/System/event_bus.scala Thu Feb 20 14:36:17 2014 +0100
@@ -7,6 +7,7 @@
package isabelle
+
import scala.actors.Actor, Actor._
import scala.collection.mutable.ListBuffer