diff --git a/boost/iostreams/device/mapped_file.hpp b/boost/iostreams/device/mapped_file.hpp
index aae9dab..be656ef 100644
--- a/boost/iostreams/device/mapped_file.hpp
+++ b/boost/iostreams/device/mapped_file.hpp
@@ -4,6 +4,9 @@
 // Distributed under the Boost Software License, Version 1.0. (See accompanying
 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
 
+#ifndef BOOST_IOSTREAMS_MAPPED_FILE_HPP_INCLUDED
+#define BOOST_IOSTREAMS_MAPPED_FILE_HPP_INCLUDED
+
 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
 # pragma once
 #endif
@@ -591,3 +594,5 @@ operator^=(mapped_file::mapmode& a, mapped_file::mapmode b)
 } } // End namespaces iostreams, boost.
 
 #include <boost/config/abi_suffix.hpp> // pops abi_suffix.hpp pragmas
+
+#endif // #ifndef BOOST_IOSTREAMS_MAPPED_FILE_HPP_INCLUDED