diff --git a/src/serialization/json_utils.h b/src/serialization/json_utils.h
index 35bcc033..24f5c11a 100644
--- a/src/serialization/json_utils.h
+++ b/src/serialization/json_utils.h
@@ -2,6 +2,8 @@
 // Distributed under the MIT/X11 software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+#pragma once
+
 #include <sstream>
 #include "json_archive.h"