diff --git a/util/cast_util.h b/util/cast_util.h
index b42d5d6c4..2dc8138ab 100644
--- a/util/cast_util.h
+++ b/util/cast_util.h
@@ -3,6 +3,8 @@
 //  COPYING file in the root directory) and Apache 2.0 License
 //  (found in the LICENSE.Apache file in the root directory).
 
+#pragma once
+
 namespace rocksdb {
 // The helper function to assert the move from dynamic_cast<> to
 // static_cast<> is correct. This function is to deal with legacy code.