diff --git a/configuration.py b/configuration.py
index ac0550b..79ee773 100644
--- a/configuration.py
+++ b/configuration.py
@@ -1,6 +1,7 @@
 # This file is part product_purchase_sequence module for Tryton.
 # The COPYRIGHT file at the top level of this repository contains
 # the full copyright notices and license terms.
+from trytond.model import fields
 from trytond.pool import PoolMeta
 
 __all__ = [