diff --git a/tools/ndnsec/list.cpp b/tools/ndnsec/list.cpp
index 1aa2d4e..fbe1140 100644
--- a/tools/ndnsec/list.cpp
+++ b/tools/ndnsec/list.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2013-2019 Regents of the University of California.
+ * Copyright (c) 2013-2020 Regents of the University of California.
  *
  * This file is part of ndn-cxx library (NDN C++ library with eXperimental eXtensions).
  *
@@ -19,6 +19,7 @@
  * See AUTHORS.md for complete list of ndn-cxx authors and contributors.
  */
 
+#include "accumulator.hpp"
 #include "ndnsec.hpp"
 #include "util.hpp"