diff --git a/tools/ndnsec/cert-dump.cpp b/tools/ndnsec/cert-dump.cpp
index b5ac12f..8237f5d 100644
--- a/tools/ndnsec/cert-dump.cpp
+++ b/tools/ndnsec/cert-dump.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2022 Regents of the University of California.
+ * Copyright (c) 2013-2023 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -27,8 +27,7 @@
 #include <boost/date_time/posix_time/posix_time_duration.hpp>
 #endif // BOOST_VERSION < 106700
 
-namespace ndn {
-namespace ndnsec {
+namespace ndn::ndnsec {
 
 int
 ndnsec_cert_dump(int argc, char** argv)
@@ -142,5 +141,4 @@
   return 0;
 }
 
-} // namespace ndnsec
-} // namespace ndn
+} // namespace ndn::ndnsec