diff --git a/src/detail/challenge-encoder.hpp b/src/detail/challenge-encoder.hpp
index a8baa57..2013061 100644
--- a/src/detail/challenge-encoder.hpp
+++ b/src/detail/challenge-encoder.hpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2017-2020, Regents of the University of California.
+/*
+ * Copyright (c) 2017-2021, Regents of the University of California.
  *
  * This file is part of ndncert, a certificate management system based on NDN.
  *
@@ -24,7 +24,6 @@
 #include "detail/ca-request-state.hpp"
 #include "requester-request.hpp"
 
-namespace ndn {
 namespace ndncert {
 namespace challengetlv {
 
@@ -36,6 +35,5 @@
 
 } // namespace challengetlv
 } // namespace ndncert
-} // namespace ndn
 
-#endif // NDNCERT_DETAIL_CHALLENGE_ENCODER_HPP
\ No newline at end of file
+#endif // NDNCERT_DETAIL_CHALLENGE_ENCODER_HPP