diff --git a/trytond/osv/orm.py b/trytond/osv/orm.py
index 79f0de947d..74f66ed441 100644
--- a/trytond/osv/orm.py
+++ b/trytond/osv/orm.py
@@ -1861,6 +1861,16 @@ class ORM(object):
             fargs = args[i][0].split('.', 1)
             field = table._columns.get(fargs[0], False)
             if not field:
+                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 len(fargs) > 1: