diff --git a/examples/producer.cpp b/examples/producer.cpp
index ac3165e..a1f3422 100644
--- a/examples/producer.cpp
+++ b/examples/producer.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
-/**
- * Copyright (c) 2014-2018, Regents of the University of California
+/*
+ * Copyright (c) 2014-2020, Regents of the University of California
  *
  * NAC library is free software: you can redistribute it and/or modify it under the
  * terms of the GNU Lesser General Public License as published by the Free Software
@@ -19,6 +19,7 @@
 
 #include <ndn-cxx/face.hpp>
 #include <ndn-cxx/security/key-chain.hpp>
+#include <ndn-cxx/security/signing-helpers.hpp>
 #include <ndn-cxx/security/validator-config.hpp>
 
 #include "encryptor.hpp"