diff --git a/tests/io-key-chain-fixture.hpp b/tests/io-key-chain-fixture.hpp
index fa5beab..c88a700 100644
--- a/tests/io-key-chain-fixture.hpp
+++ b/tests/io-key-chain-fixture.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2014-2020, Regents of the University of California
+ * Copyright (c) 2014-2022, Regents of the University of California
  *
  * NAC library is free software: you can redistribute it and/or modify it under the
  * terms of the GNU Lesser General Public License as published by the Free Software
@@ -25,9 +25,7 @@
 
 #include <boost/asio/io_service.hpp>
 
-namespace ndn {
-namespace nac {
-namespace tests {
+namespace ndn::nac::tests {
 
 class IoKeyChainFixture : public ClockFixture, public KeyChainFixture
 {
@@ -49,8 +47,6 @@
   boost::asio::io_service m_io;
 };
 
-} // namespace tests
-} // namespace nac
-} // namespace ndn
+} // namespace ndn::nac::tests
 
 #endif // NAC_TESTS_IO_KEY_CHAIN_FIXTURE_HPP