Index: any.hpp
===================================================================
--- any.hpp	(revision 43863)
+++ any.hpp	(working copy)
@@ -127,6 +127,8 @@
 
             ValueType held;
 
+        private: // intentionally left unimplemented
+            holder & operator=(const holder &);
         };
 
 #ifndef BOOST_NO_MEMBER_TEMPLATE_FRIENDS