diff --git a/akka-actor/src/main/scala/akka/actor/FSM.scala b/akka-actor/src/main/scala/akka/actor/FSM.scala
index fd3c9ab2e3..ac5b21e203 100644
--- a/akka-actor/src/main/scala/akka/actor/FSM.scala
+++ b/akka-actor/src/main/scala/akka/actor/FSM.scala
@@ -423,6 +423,7 @@ trait FSM[S, D] extends ListenerManagement {
    */
   private val handleEventDefault: StateFunction = {
     case Event(value, stateData) ⇒
+      EventHandler.warning(this, "unhandled event " + value + " in state " + stateName)
       stay
   }
   private var handleEvent: StateFunction = handleEventDefault