Index: shared_ptr_helper.hpp
===================================================================
--- shared_ptr_helper.hpp	(リビジョン 53717)
+++ shared_ptr_helper.hpp	(作業コピー)
@@ -126,10 +126,36 @@
 
         if(it == m_pointers->end()){
             s.reset(r);
-            m_pointers->insert(collection_type::value_type(od,s));
+            // make shared_ptr. 
+            // data member pn of shared_ptr sp shared with s,
+            // but data member px of shared_ptr sp is od.
+            shared_ptr<void> sp(s, const_cast<void *>(od)); // aliasing
+            // insert shared_ptr of the most derived object into m_pointers.
+            m_pointers->insert(collection_type::value_type(od,sp));
         }
         else{
-            s = static_pointer_cast<T>((*it).second);
+            const boost::serialization::extended_type_info * true_type 
+                = boost::serialization::type_info_implementation<T>::type
+                    ::get_const_instance().get_derived_extended_type_info(*r);
+            if(NULL == true_type)
+                boost::serialization::throw_exception(
+                    boost::archive::archive_exception(
+                        boost::archive::archive_exception::unregistered_class
+                    )
+                );
+            const boost::serialization::extended_type_info * this_type
+                = & boost::serialization::type_info_implementation<T>::type
+                        ::get_const_instance();
+            // get this type pointer from pointer to the most derived object.
+            void * vp = void_upcast(
+                *true_type, 
+                *this_type, 
+                (*it).second.get()
+            );
+            // make and set shared_ptr.
+            // data member pn of shared_ptr s shared with (*it).second,
+            // but data member px of shared_ptr s is vp.
+            s = shared_ptr<T>((*it).second, static_cast<T *>(vp)); // aliasing
         }
     }
     void append(const boost_132::shared_ptr<void> & t){