diff --git a/src/lp/nack.cpp b/src/lp/nack.cpp
index c31a114..56b183d 100644
--- a/src/lp/nack.cpp
+++ b/src/lp/nack.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2013-2015 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).
  *
@@ -26,6 +26,8 @@
 namespace ndn {
 namespace lp {
 
+Nack::Nack() = default;
+
 Nack::Nack(const Interest& interest)
   : m_interest(interest)
 {
@@ -37,4 +39,4 @@
 }
 
 } // namespace lp
-} // namespace ndn
\ No newline at end of file
+} // namespace ndn