diff --git a/gluon/sqlhtml.py b/gluon/sqlhtml.py
index 62e53507..cb85158d 100644
--- a/gluon/sqlhtml.py
+++ b/gluon/sqlhtml.py
@@ -1768,7 +1768,7 @@ class SQLFORM(FORM):
                     iso_format = {'_data-w2p_date_format' : '%Y-%m-%d'}
                     value_input = SQLFORM.widgets.date.widget(field, field.default, _id=_id, **iso_format)
                 elif field.type == 'datetime':
-                    iso_format = iso_format = {'_data-w2p_datetime_format' : '%Y-%m-%d %H:%M:%S'}
+                    iso_format = {'_data-w2p_datetime_format' : '%Y-%m-%d %H:%M:%S'}
                     value_input = SQLFORM.widgets.datetime.widget(field, field.default, _id=_id, **iso_format)
                 elif (field.type.startswith('reference ') or
                       field.type.startswith('list:reference ')) and \