--- optional.hpp        2007-10-02 11:39:09.000000000 +0800
+++ optional.hpp        2007-10-23 18:08:06.000000000 +0800
@@ -550,7 +550,7 @@
     //  (NOTE: On BCB, this operator is not actually called and left is left UNMODIFIED in case of a throw)
     optional& operator= ( optional const& rhs )
       {
-        this->assign( rhs ) ;
+        this->assign( static_cast<base const&>(rhs) ) ;
         return *this ;
       }