diff --git a/include/boost/python/detail/not_specified.hpp b/include/boost/python/detail/not_specified.hpp
new file mode 100644
index 00000000..ce1b280d
--- /dev/null
+++ b/include/boost/python/detail/not_specified.hpp
@@ -0,0 +1,15 @@
+// Copyright David Abrahams 2002. Permission to copy, use,
+// modify, sell and distribute this software is granted provided this
+// copyright notice appears in all copies. This software is provided
+// "as is" without express or implied warranty, and with no claim as
+// to its suitability for any purpose.
+#ifndef NOT_SPECIFIED_DWA2002321_HPP
+# define NOT_SPECIFIED_DWA2002321_HPP
+
+namespace boost { namespace python { namespace detail { 
+
+  struct not_specified {};
+
+}}} // namespace boost::python::detail
+
+#endif // NOT_SPECIFIED_DWA2002321_HPP