diff --git a/src/simulator/default-simulator-impl.cc b/src/simulator/default-simulator-impl.cc
index 670413c71..ec3db6aac 100644
--- a/src/simulator/default-simulator-impl.cc
+++ b/src/simulator/default-simulator-impl.cc
@@ -144,7 +144,7 @@ DefaultSimulatorImpl::Next (void) const
 void
 DefaultSimulatorImpl::Run (void)
 {
-
+  m_stop = false;
   while (!m_events->IsEmpty () && !m_stop) 
     {
       ProcessOneEvent ();
diff --git a/src/simulator/realtime-simulator-impl.cc b/src/simulator/realtime-simulator-impl.cc
index bd49d028d..5cc3c10b1 100644
--- a/src/simulator/realtime-simulator-impl.cc
+++ b/src/simulator/realtime-simulator-impl.cc
@@ -421,6 +421,7 @@ RealtimeSimulatorImpl::Run (void)
   NS_ASSERT_MSG (m_running == false, 
                  "RealtimeSimulatorImpl::Run(): Simulator already running");
 
+  m_stop = false;
   m_running = true;
   m_synchronizer->SetOrigin (m_currentTs);