diff --git a/src/util/backports-optional.hpp b/src/util/backports-optional.hpp
index d00cb60..29862b1 100644
--- a/src/util/backports-optional.hpp
+++ b/src/util/backports-optional.hpp
@@ -1,5 +1,5 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
+/*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
diff --git a/src/util/backports-ostream-joiner.hpp b/src/util/backports-ostream-joiner.hpp
index 384f24a..24a161c 100644
--- a/src/util/backports-ostream-joiner.hpp
+++ b/src/util/backports-ostream-joiner.hpp
@@ -1,5 +1,5 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
+/*
  * Copyright (c) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
diff --git a/src/util/signal-emit.hpp b/src/util/signal-emit.hpp
index 17eacd0..a28872c 100644
--- a/src/util/signal-emit.hpp
+++ b/src/util/signal-emit.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) 2013-2017 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *