Index: wcs/fields.py
===================================================================
--- wcs/fields.py	(révision 2193)
+++ wcs/fields.py	(copie de travail)
@@ -583,6 +583,11 @@
         except TypeError:
             return ''
 
+    def add_to_form(self, form, value=None):
+        if value and type(value) is not str:
+             value = self.convert_value_to_str(value)
+        WidgetField.add_to_form(self, form, value=value)
+
     def add_to_view_form(self, form, value = None):
         value = localstrftime(value)
         return WidgetField.add_to_view_form(self, form, value = value)