diff --git a/src/main/scala/viper/server/vsi/VerificationServer.scala b/src/main/scala/viper/server/vsi/VerificationServer.scala
index ec777d9..10f4491 100644
--- a/src/main/scala/viper/server/vsi/VerificationServer.scala
+++ b/src/main/scala/viper/server/vsi/VerificationServer.scala
@@ -241,7 +241,12 @@ trait VerificationServer extends Post {
 
             // FIXME This assumes that someone will actually complete the verification job queue.
             // FIXME Could we guarantee that the client won't forget to do this?
-            ver_handle.queue.watchCompletion()
+            ver_handle match {
+              case VerHandle(null, null, null, _) =>
+                Future.successful(Done)
+              case _ =>
+                ver_handle.queue.watchCompletion()
+            }
         })
     }
   }
@@ -299,8 +304,13 @@ trait VerificationServer extends Post {
         handle_future.flatMap {
           case AstHandle(actor, _, _, _) =>
             (actor ? VerificationProtocol.StopAstConstruction).mapTo[String]
+          case VerHandle(null, _, _, _) =>
+            Future.successful("Job had no actor.")
           case VerHandle(actor, _, _, _) =>
             (actor ? VerificationProtocol.StopVerification).mapTo[String]
+        }.recover {
+          case _: akka.pattern.AskTimeoutException =>
+            "Job actor already terminated."
         }
       } toList
     val overall_interrupt_future: Future[List[String]] = Future.sequence(interrupt_future_list)