diff --git a/include/boost/python/return_opaque_pointer.hpp b/include/boost/python/return_opaque_pointer.hpp
index 2109d4ec..6a3af9be 100644
--- a/include/boost/python/return_opaque_pointer.hpp
+++ b/include/boost/python/return_opaque_pointer.hpp
@@ -15,39 +15,43 @@
 # include <boost/mpl/if.hpp>
 
 namespace boost { namespace python {
-    namespace detail {
-        template <class Pointer>
-        struct opaque_conversion_holder {
-            inline PyObject *operator () (Pointer p) {
-                static opaque_pointer_converter<Pointer> converter (
-                    typeid (Pointer).name());
 
-                return converter.convert(p);
-            }
-        };
+namespace detail
+{
+  template <class Pointer>
+  struct opaque_conversion_holder
+  {
+      inline PyObject *operator()(Pointer p) const
+      {
+          static opaque_pointer_converter<Pointer> converter (
+              typeid (Pointer).name());
 
-        template <class R>
-        struct return_opaque_pointer_requires_a_pointer_type
+          return converter.convert(p);
+      }
+  };
+
+  template <class R>
+  struct return_opaque_pointer_requires_a_pointer_type
 # if defined(__GNUC__) && __GNUC__ >= 3 || defined(__EDG__)
-        {}
+  {}
 # endif
-        ;
-    }
+  ;
+}
     
-    struct return_opaque_pointer
+struct return_opaque_pointer
+{
+    template <class R>
+    struct apply
     {
-        template <class R>
-        struct apply
-        {
-            BOOST_STATIC_CONSTANT(
-                bool, ok = is_pointer<R>::value);
+        BOOST_STATIC_CONSTANT(
+            bool, ok = is_pointer<R>::value);
         
-            typedef typename mpl::if_c<
-                ok
-                , detail::opaque_conversion_holder<R>
-                , detail::return_opaque_pointer_requires_a_pointer_type<R>
-            >::type type;
-        };
+        typedef typename mpl::if_c<
+            ok
+          , detail::opaque_conversion_holder<R>
+          , detail::return_opaque_pointer_requires_a_pointer_type<R>
+        >::type type;
     };
+};
 }} // namespace boost::python
 # endif // RETURN_OPAQUE_POINTER_HPP_