diff --git a/addons/website_sale/models/sale_order.py b/addons/website_sale/models/sale_order.py
index 4c942c2da54..8cc155b43a0 100644
--- a/addons/website_sale/models/sale_order.py
+++ b/addons/website_sale/models/sale_order.py
@@ -129,9 +129,16 @@ class website(orm.Model):
     def sale_get_order(self, cr, uid, ids, force_create=False, code=None, update_pricelist=None, context=None):
         sale_order_obj = self.pool['sale.order']
         sale_order_id = request.session.get('sale_order_id')
-        sale_order = sale_order_obj.browse(cr, SUPERUSER_ID, sale_order_id, context=context)
+        sale_order = None
+
+        # Test validity of the sale_order_id
+        if sale_order_id and sale_order_obj.exists(cr, SUPERUSER_ID, sale_order_id, context=context):
+            sale_order = sale_order_obj.browse(cr, SUPERUSER_ID, sale_order_id, context=context)
+        else:
+            sale_order_id = None
+
         # create so if needed
-        if not sale_order.exists() and (force_create or code):
+        if not sale_order_id and (force_create or code):
             # TODO cache partner_id session
             partner = self.pool['res.users'].browse(cr, SUPERUSER_ID, uid, context=context).partner_id
 
@@ -148,7 +155,7 @@ class website(orm.Model):
                 request.session['sale_order_id'] = sale_order_id
                 sale_order = sale_order_obj.browse(cr, SUPERUSER_ID, sale_order_id, context=context)
 
-        if sale_order.exists():
+        if sale_order_id:
             # TODO cache partner_id session
             partner = self.pool['res.users'].browse(cr, SUPERUSER_ID, uid, context=context).partner_id
             # check for change of pricelist with a coupon