diff --git a/utils/counting-policy.h b/utils/counting-policy.h
index b7d992e..d8cfe07 100644
--- a/utils/counting-policy.h
+++ b/utils/counting-policy.h
@@ -24,6 +24,8 @@
 #include <boost/intrusive/options.hpp>
 #include <boost/intrusive/list.hpp>
 
+namespace ns3
+{
 namespace ndnSIM
 {
 
@@ -103,5 +105,6 @@
 };
 
 } // ndnSIM
+} // ns3
 
 #endif // COUNTING_POLICY_H_