diff --git a/example/sse.cc b/example/sse.cc
index 7aa7ad7..cce1e6b 100644
--- a/example/sse.cc
+++ b/example/sse.cc
@@ -11,6 +11,7 @@
 #include <httplib.h>
 #include <iostream>
 #include <mutex>
+#include <sstream>
 #include <thread>
 
 using namespace httplib;