diff --git a/account_constraints/account_constraints.py b/account_constraints/account_constraints.py
index b8a4c267c..8190e9854 100644
--- a/account_constraints/account_constraints.py
+++ b/account_constraints/account_constraints.py
@@ -48,7 +48,7 @@ class AccountMoveLine(orm.Model):
         for line in self.browse(cr, uid, ids, context=context):
             if line.invoice:
                 err_msg = (_('Invoice name (id): %s (%s)') %
-                            (line.invoice.name, str(line.invoice.id)))
+                            (line.invoice.name, line.invoice.id))
                 raise osv.except_osv(
                     _('Error'),
                     _('You cannot do this on an entry generated by an invoice. You must '
@@ -59,7 +59,7 @@ class AccountMoveLine(orm.Model):
         for line in self.browse(cr, uid, ids, context=context):
             if line.statement_id:
                 err_msg = (_('Bank statement name (id): %s (%s)') %
-                            (line.statement_id.name, str(line.statement_id.id)))
+                            (line.statement_id.name, line.statement_id.id))
                 raise osv.except_osv(
                     _('Error'),
                     _('You cannot do this on an entry generated by a bank statement. '
@@ -100,7 +100,7 @@ class AccountMoveLine(orm.Model):
         if not context.get('from_parent_object', False):
             self._check_invoice_related_move(cr, uid, ids, context=context)
             self._check_statement_related_move(cr, uid, ids, context=context)
-        return super(AccountMoveLine, self).write(cr, uid, ids, vals, 
+        return super(AccountMoveLine, self).write(cr, uid, ids, vals,
             context=context, check=check, update_check=update_check)
 
     def _check_currency_and_amount(self, cr, uid, ids, context=None):