Index: boost/units/base_dimension.hpp
===================================================================
--- boost/units/base_dimension.hpp	(revision 70997)
+++ boost/units/base_dimension.hpp	(working copy)
@@ -77,6 +77,12 @@
         typedef Derived type;
 
     private:
+        // Check in C++0x if an ordinal is registered for two different types.
+        // INTERNAL ONLY
+        friend 
+        Derived*
+        check_double_register(units::base_dimension_ordinal<N>&) { return 0; }
+
         /// Register this ordinal
         /// INTERNAL ONLY
         friend detail::yes