diff --git a/bin/addons/base/ir/ir_model.py b/bin/addons/base/ir/ir_model.py
index df73edd108b..91360668243 100644
--- a/bin/addons/base/ir/ir_model.py
+++ b/bin/addons/base/ir/ir_model.py
@@ -204,7 +204,7 @@ class ir_model_fields(osv.osv):
         'select_level': fields.selection([('0','Not Searchable'),('1','Always Searchable'),('2','Advanced Search')],'Searchable', required=True),
         'translate': fields.boolean('Translate'),
         'size': fields.integer('Size'),
-        'state': fields.selection([('manual','Custom Field'),('base','Base Field')],'Manualy Created', required=True),
+        'state': fields.selection([('manual','Custom Field'),('base','Base Field')],'Manualy Created', required=True, readonly=True),
         'on_delete': fields.selection([('cascade','Cascade'),('set null','Set NULL')], 'On delete', help='On delete property for many2one fields'),
         'domain': fields.char('Domain', size=256),
         'groups': fields.many2many('res.groups', 'ir_model_fields_group_rel', 'field_id', 'group_id', 'Groups'),