diff --git a/http/http_connection.hpp b/http/http_connection.hpp
index d061973..6494586 100644
--- a/http/http_connection.hpp
+++ b/http/http_connection.hpp
@@ -35,7 +35,8 @@
 {
     json_html_util::dumpHtml(res.body(), res.jsonValue);
 
-    res.addHeader("Content-Type", "text/html;charset=UTF-8");
+    res.addHeader(boost::beast::http::field::content_type,
+                  "text/html;charset=UTF-8");
 }
 
 static int connectionCount = 0;