diff --git a/src/util/shared_mutex.h b/src/util/shared_mutex.h
index 9c98630fa..2c44fcede 100644
--- a/src/util/shared_mutex.h
+++ b/src/util/shared_mutex.h
@@ -10,6 +10,7 @@
    Hinnant. The proposal is also part of the Boost library which is
    licensed under http://www.boost.org/LICENSE_1_0.txt
 */
+#pragma once
 #include <climits>
 #include "util/thread.h"