diff --git a/addons/purchase/purchase.py b/addons/purchase/purchase.py
index d70ea13d39b..dfdf85080fe 100644
--- a/addons/purchase/purchase.py
+++ b/addons/purchase/purchase.py
@@ -425,6 +425,7 @@ class purchase_order(osv.osv):
                 'invoice_state': istate,
                 'purchase_id': order.id,
                 'company_id': order.company_id.id,
+                'move_lines' : [],
             })
             todo_moves = []
             for order_line in order.order_line:
@@ -800,4 +801,4 @@ class procurement_order(osv.osv):
 
 procurement_order()
 
-# vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4:
\ No newline at end of file
+# vim:expandtab:smartindent:tabstop=4:softtabstop=4:shiftwidth=4: