diff --git a/.isort.cfg b/.isort.cfg
new file mode 100644
index 0000000000..e1c6495da9
--- /dev/null
+++ b/.isort.cfg
@@ -0,0 +1,3 @@
+[settings]
+multi_line_output=4
+known_first_party=trytond
diff --git a/__init__.py b/__init__.py
index 4dda3298c5..4887bae595 100644
--- a/__init__.py
+++ b/__init__.py
@@ -2,8 +2,8 @@
 # this repository contains the full copyright notices and license terms.
 
 from trytond.pool import Pool
-from . import dunning
-from . import account
+
+from . import account, dunning
 
 
 def register():
diff --git a/dunning.py b/dunning.py
index ba704add58..02a7962c45 100644
--- a/dunning.py
+++ b/dunning.py
@@ -2,13 +2,12 @@
 # this repository contains the full copyright notices and license terms.
 from collections import defaultdict
 
-from trytond.model import ModelView, ModelSQL, DeactivableMixin, fields, Unique
-from trytond.pool import PoolMeta, Pool
+from trytond.model import DeactivableMixin, ModelSQL, ModelView, Unique, fields
+from trytond.modules.currency.fields import Monetary
+from trytond.pool import Pool, PoolMeta
 from trytond.pyson import Eval
 from trytond.transaction import Transaction
 
-from trytond.modules.currency.fields import Monetary
-
 
 class Fee(DeactivableMixin, ModelSQL, ModelView):
     'Account Dunning Fee'
diff --git a/setup.py b/setup.py
index 703ee2dc23..7b120fbe90 100755
--- a/setup.py
+++ b/setup.py
@@ -6,7 +6,8 @@ import io
 import os
 import re
 from configparser import ConfigParser
-from setuptools import setup, find_packages
+
+from setuptools import find_packages, setup
 
 
 def read(fname):
diff --git a/tests/__init__.py b/tests/__init__.py
index 8b0f92b4c0..010ad936a7 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -2,7 +2,8 @@
 # this repository contains the full copyright notices and license terms.
 
 try:
-    from trytond.modules.account_dunning_fee.tests.test_account_dunning_fee import suite  # noqa: E501
+    from trytond.modules.account_dunning_fee.tests.test_account_dunning_fee import \
+        suite  # noqa: E501
 except ImportError:
     from .test_account_dunning_fee import suite
 
diff --git a/tests/test_account_dunning_fee.py b/tests/test_account_dunning_fee.py
index 89220cf4fe..70434b8ac2 100644
--- a/tests/test_account_dunning_fee.py
+++ b/tests/test_account_dunning_fee.py
@@ -1,13 +1,12 @@
 # This file is part of Tryton.  The COPYRIGHT file at the top level of
 # this repository contains the full copyright notices and license terms.
 
+import doctest
 import unittest
 
-import doctest
-
-from trytond.tests.test_tryton import ModuleTestCase
+from trytond.tests.test_tryton import (
+    ModuleTestCase, doctest_checker, doctest_teardown)
 from trytond.tests.test_tryton import suite as test_suite
-from trytond.tests.test_tryton import doctest_teardown, doctest_checker
 
 
 class AccountDunningFeeTestCase(ModuleTestCase):