diff --git a/tools/ndncert-client.cpp b/tools/ndncert-client.cpp
index 86ff60f..7f082d8 100644
--- a/tools/ndncert-client.cpp
+++ b/tools/ndncert-client.cpp
@@ -22,6 +22,8 @@
 #include "challenge-module.hpp"
 #include "logging.hpp"
 
+#include <iostream>
+
 #include <boost/program_options/options_description.hpp>
 #include <boost/program_options/variables_map.hpp>
 #include <boost/program_options/parsers.hpp>