diff --git a/Trigger/TrigEvent/TrigNavStructure/Root/StandaloneNavigation.cxx b/Trigger/TrigEvent/TrigNavStructure/Root/StandaloneNavigation.cxx
index 7c55fc0153cb583b30e4cafcfb6869f3859d7788..c7aa30f5cf720112561011c21299eaa80aefdfaa 100644
--- a/Trigger/TrigEvent/TrigNavStructure/Root/StandaloneNavigation.cxx
+++ b/Trigger/TrigEvent/TrigNavStructure/Root/StandaloneNavigation.cxx
@@ -2,6 +2,10 @@
   Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
 */
 
+
+// System include(s):
+#include <iostream>
+
 #include "TrigNavStructure/StandaloneNavigation.h"
 #include "TrigNavStructure/TypelessHolder.h"