diff --git a/openerp/osv/expression.py b/openerp/osv/expression.py
index 417d03c4bb0..ecf01d86618 100644
--- a/openerp/osv/expression.py
+++ b/openerp/osv/expression.py
@@ -729,6 +729,8 @@ class expression(object):
             """ Return a domain implementing the child_of operator for [(left,child_of,ids)],
                 either as a range using the parent_left/right tree lookup fields
                 (when available), or as an expanded [(left,in,child_ids)] """
+            if not ids:
+                return FALSE_DOMAIN
             if left_model._parent_store and (not left_model.pool._init):
                 # TODO: Improve where joins are implemented for many with '.', replace by:
                 # doms += ['&',(prefix+'.parent_left','<',o.parent_right),(prefix+'.parent_left','>=',o.parent_left)]