diff --git a/trytond/osv/orm.py b/trytond/osv/orm.py
index a2cf70f79a..db6c2dd397 100644
--- a/trytond/osv/orm.py
+++ b/trytond/osv/orm.py
@@ -2058,19 +2058,9 @@ class ORM(object):
             fargs = args[i][0].split('.', 1)
             field = table._columns.get(fargs[0], False)
             if not field:
-                # XXX must find a solution for long id list
-                if args[i][0] == 'id' and args[i][1] == 'child_of':
-                    ids2 = args[i][2]
-                    def _rec_get(ids, table, parent):
-                        if not ids:
-                            return []
-                        ids2 = table.search(cursor, user,
-                                [(parent, 'in', ids)], context=context)
-                        return ids2 + _rec_get(ids2, table, parent)
-                    args[i] = (args[i][0], 'in', ids2 + \
-                            _rec_get(ids2, table, table._parent_name), table)
-                i += 1
-                continue
+                if fargs[0] in self._inherit_fields:
+                    table = self.pool.get(self._inherit_fields[args[i][0]][0])
+                    field = table._columns.get(fargs[0], False)
             if len(fargs) > 1:
                 if field._type == 'many2one':
                     args[i] = (fargs[0], 'inselect',