Fixes SI-4759

1 files changed, 17 insertions, 10 deletions

diff --git a/src/actors/scala/actors/Actor.scala b/src/actors/scala/actors/Actor.scala
index 25cfbf7865..57e107538c 100644
--- a/src/actors/scala/actors/Actor.scala
+++ b/src/actors/scala/actors/Actor.scala
@@ -590,20 +590,27 @@ trait Actor extends AbstractActor with ReplyReactor with ActorCanReply with Inpu
             receiveTimeout
           } else {
             if (onTimeout.isEmpty) {
-              waitingFor = f
-              received = None
-              isSuspended = true
+              if (!f.isDefinedAt(TIMEOUT))
+                sys.error("unhandled timeout")
+
               val thisActor = this
               onTimeout = Some(new TimerTask {
-                def run() { thisActor.send(TIMEOUT, thisActor) }
+                def run() {
+                  thisActor.send(TIMEOUT, thisActor)
+                }
               })
               Actor.timer.schedule(onTimeout.get, msec)
-              scheduler.managedBlock(blocker)
-              drainSendBuffer(mailbox)
-              // keep going
-              () => {}
-            } else
-              sys.error("unhandled timeout")
+            }
+
+            // It is possible that !onTimeout.isEmpty, but TIMEOUT is not yet in mailbox
+            // See SI-4759
+            waitingFor = f
+            received = None
+            isSuspended = true
+            scheduler.managedBlock(blocker)
+            drainSendBuffer(mailbox)
+            // keep going
+            () => {}
           }
         }
         todo()