diff --git a/addons/sale/sale.py b/addons/sale/sale.py
index 7de5eb906e0..fa95f169d26 100644
--- a/addons/sale/sale.py
+++ b/addons/sale/sale.py
@@ -627,6 +627,12 @@ class sale_order(osv.osv):
         return self.write(cr, uid, ids, {'state': 'done'}, context=context)
 
     def onchange_fiscal_position(self, cr, uid, ids, fiscal_position, order_lines, context=None):
+        '''Update taxes of order lines for each line where a product is defined
+
+        :param list ids: not used
+        :param int fiscal_position: sale order fiscal position
+        :param list order_lines: command list for one2many write method
+        '''
         order_line = []
         fiscal_obj = self.pool.get('account.fiscal.position')
         product_obj = self.pool.get('product.product')
@@ -640,14 +646,13 @@ class sale_order(osv.osv):
             # create    (0, 0,  { fields })
             # update    (1, ID, { fields })
             if line[0] in [0, 1]:
-                taxes_id = None
+                prod = None
                 if line[2].get('product_id'):
-                    taxes_id = product_obj.browse(cr, uid, line[2]['product_id'], context=context).taxes_id
+                    prod = product_obj.browse(cr, uid, line[2]['product_id'], context=context)
                 elif line[1]:
-                    # don't change taxes if they are no product defined
-                    taxes_id = line_obj.browse(cr, uid, line[1], context=context).product_id.taxes_id
-                if taxes_id:
-                    line[2]['tax_id'] = [[6, 0, fiscal_obj.map_tax(cr, uid, fpos, taxes_id)]]
+                    prod =  line_obj.browse(cr, uid, line[1], context=context).product_id
+                if prod and prod.taxes_id:
+                    line[2]['tax_id'] = [[6, 0, fiscal_obj.map_tax(cr, uid, fpos, prod.taxes_id)]]
                 order_line.append(line)
 
             # link      (4, ID)
@@ -655,9 +660,11 @@ class sale_order(osv.osv):
             elif line[0] in [4, 6]:
                 line_ids = line[0] == 4 and [line[1]] or line[2]
                 for line_id in line_ids:
-                    taxes_id = line_obj.browse(cr, uid, line_id, context=context).product_id.taxes_id
-                    order_line.append([1, line_id, {'tax_id': [[6, 0, fiscal_obj.map_tax(cr, uid, fpos, taxes_id)]]}])
-
+                    prod = line_obj.browse(cr, uid, line_id, context=context).product_id
+                    if prod and prod.taxes_id:
+                        order_line.append([1, line_id, {'tax_id': [[6, 0, fiscal_obj.map_tax(cr, uid, fpos, prod.taxes_id)]]}])
+                    else:
+                        order_line.append([4, line_id])
             else:
                 order_line.append(line)
         return {'value': {'order_line': order_line}}