diff --git a/src/security/validator-null.hpp b/src/security/validator-null.hpp
index 34b18c8..36448af 100644
--- a/src/security/validator-null.hpp
+++ b/src/security/validator-null.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /**
- * Copyright (c) 2013-2014 Regents of the University of California.
+ * Copyright (c) 2013-2016 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -28,6 +28,7 @@
 #include "validator.hpp"
 
 namespace ndn {
+namespace security {
 
 class ValidatorNull : public Validator
 {
@@ -59,6 +60,10 @@
   }
 };
 
+} // namespace security
+
+using security::ValidatorNull;
+
 } // namespace ndn
 
 #endif //NDN_SECURITY_VALIDATOR_NULL_HPP