--- boost/date_time/constrained_value.hpp
+++ boost/date_time/constrained_value.hpp
@@ -40,6 +40,7 @@
     //    typedef except_type exception_type;
     constrained_value(value_type value) 
     {
+      value_ = value;
       assign(value);
     };
     constrained_value& operator=(value_type v)