diff --git a/addons/account/invoice.py b/addons/account/invoice.py
index 93f91811b0f..86ea0fbd2b2 100644
--- a/addons/account/invoice.py
+++ b/addons/account/invoice.py
@@ -804,11 +804,10 @@ class account_invoice_line(osv.osv):
         context.update({'lang': lang})
         res = self.pool.get('product.product').browse(cr, uid, product, context=context)
         taxep=None
-        if partner_id:
-            lang=self.pool.get('res.partner').read(cr, uid, [partner_id])[0]['lang']
+        lang=self.pool.get('res.partner').read(cr, uid, [partner_id])[0]['lang']
         tax_obj = self.pool.get('account.tax')
         if type in ('out_invoice', 'out_refund'):
-            taxep = self.pool.get('res.partner').browse(cr, uid, partner_id).property_account_supplier_tax
+            taxep = self.pool.get('res.partner').browse(cr, uid, partner_id).property_account_tax
             if not taxep or not taxep.id:
                 tax_id = map(lambda x: x.id, res.taxes_id)
             else:
@@ -817,7 +816,7 @@ class account_invoice_line(osv.osv):
                     if not t.tax_group==taxep.tax_group:
                         tax_id.append(t.id)
         else:
-            taxep = self.pool.get('res.partner').browse(cr, uid, partner_id).property_account_tax
+            taxep = self.pool.get('res.partner').browse(cr, uid, partner_id).property_account_supplier_tax
             if not taxep or not taxep.id:
                 tax_id = map(lambda x: x.id, res.supplier_taxes_id)
             else: