diff --git a/tools/ping/client/tracer.cpp b/tools/ping/client/tracer.cpp
index 7c16a4c..6b8b78f 100644
--- a/tools/ping/client/tracer.cpp
+++ b/tools/ping/client/tracer.cpp
@@ -1,6 +1,6 @@
 /* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
 /*
- * Copyright (c) 2015-2022,  Arizona Board of Regents.
+ * Copyright (c) 2015-2024,  Arizona Board of Regents.
  *
  * This file is part of ndn-tools (Named Data Networking Essential Tools).
  * See AUTHORS.md for complete list of ndn-tools authors and contributors.
@@ -22,6 +22,8 @@
 
 #include "tracer.hpp"
 
+#include <iostream>
+
 namespace ndn::ping::client {
 
 Tracer::Tracer(Ping& ping, const Options& options)