diff --git a/include/boost/checked_delete.hpp b/include/boost/checked_delete.hpp
index 92a3d0a..f2300dd 100644
--- a/include/boost/checked_delete.hpp
+++ b/include/boost/checked_delete.hpp
@@ -1,8 +1,8 @@
 #ifndef BOOST_CHECKED_DELETE_HPP_INCLUDED
 #define BOOST_CHECKED_DELETE_HPP_INCLUDED
 
-#if _MSC_VER >= 1020
-#pragma once
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
 #endif
 
 //
diff --git a/include/boost/current_function.hpp b/include/boost/current_function.hpp
index 516a394..38aeab2 100644
--- a/include/boost/current_function.hpp
+++ b/include/boost/current_function.hpp
@@ -1,8 +1,8 @@
 #ifndef BOOST_CURRENT_FUNCTION_HPP_INCLUDED
 #define BOOST_CURRENT_FUNCTION_HPP_INCLUDED
 
-#if _MSC_VER >= 1020
-#pragma once
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
 #endif
 
 //