Index: detail/packed_oprimitive.hpp
===================================================================
--- detail/packed_oprimitive.hpp	(revision 86196)
+++ detail/packed_oprimitive.hpp	(working copy)
@@ -20,6 +20,7 @@
 #include <boost/assert.hpp>
 #include <vector>
 #include <boost/mpi/allocator.hpp>
+//#include <boost/numeric/conversion/cast.hpp> // provides boost::numeric_cast
 
 namespace boost { namespace mpi {
 
@@ -81,10 +82,19 @@
     {
       unsigned int l = static_cast<unsigned int>(s.size());
       save(l);
-      if (l)
-        save_impl(s.data(),get_mpi_datatype(CharType()),s.size());
+      save_impl(s.data(),get_mpi_datatype(CharType()),s.size());
     }
 
+    void save( const boost::archive::version_type& v )
+    {
+        unsigned position = buffer_.size();
+        buffer_.resize( position+1 );
+        // Require conversion to a 1-byte int
+        // uint8_t compactV = boost::numeric_cast<uint8_t>( v ); // type safe
+        uint8_t compactV = v; // not really safe!
+        buffer_[ position ] = compactV;
+    }
+
 private:
 
     void save_impl(void const * p, MPI_Datatype t, int l)
Index: detail/packed_iprimitive.hpp
===================================================================
--- detail/packed_iprimitive.hpp	(revision 86196)
+++ detail/packed_iprimitive.hpp	(working copy)
@@ -94,11 +94,15 @@
         load(l);
         s.resize(l);
         // note breaking a rule here - could be a problem on some platform
-        if (l)
-          load_impl(const_cast<CharType *>(s.data()),
-                    get_mpi_datatype(CharType()),l);
+        load_impl(const_cast<CharType *>(s.data()),get_mpi_datatype(CharType()),l);
     }
 
+    void load( boost::archive::version_type& v )
+    {
+        v = static_cast<boost::archive::version_type>( buffer_[ position ] );
+        ++position;
+    }
+
 private:
 
     void load_impl(void * p, MPI_Datatype t, int l)