diff --git a/examples/client/helloworld_server.cc b/examples/client/helloworld_server.cc
index 309404b..0a3e4af 100644
--- a/examples/client/helloworld_server.cc
+++ b/examples/client/helloworld_server.cc
@@ -8,6 +8,7 @@
 #include <iostream>
 #include <memory>
 #include <sstream>
+#include <string>
 
 #include <absl/flags/parse.h>
 #include <absl/flags/flag.h>