diff --git a/jupytext/contentsmanager.py b/jupytext/contentsmanager.py
index d735c6c4c..f1015eb67 100644
--- a/jupytext/contentsmanager.py
+++ b/jupytext/contentsmanager.py
@@ -3,10 +3,11 @@
 import os
 from datetime import timedelta
 import nbformat
+
 try:
-    import mock
-except ImportError:
     import unittest.mock as mock
+except ImportError:
+    import mock
 from tornado.web import HTTPError
 from traitlets import Unicode, Float, Bool, Enum
 from traitlets.config import Configurable
diff --git a/tests/conftest.py b/tests/conftest.py
index fe2466a27..dcf92bfc5 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -1,8 +1,9 @@
 import pytest
+
 try:
-    import mock
-except ImportError:
     import unittest.mock as mock
+except ImportError:
+    import mock
 
 
 @pytest.fixture
diff --git a/tests/test_cli.py b/tests/test_cli.py
index ade142733..17a01d2a4 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -2,10 +2,11 @@
 import sys
 import time
 import stat
+
 try:
-    import mock
-except ImportError:
     import unittest.mock as mock
+except ImportError:
+    import mock
 import pytest
 import nbformat
 import itertools
diff --git a/tests/test_read_simple_markdown.py b/tests/test_read_simple_markdown.py
index cc64eaaba..95fdd5a41 100644
--- a/tests/test_read_simple_markdown.py
+++ b/tests/test_read_simple_markdown.py
@@ -1,7 +1,7 @@
 try:
-    import mock
-except ImportError:
     import unittest.mock as mock
+except ImportError:
+    import mock
 from nbformat.v4.nbbase import new_code_cell, new_raw_cell, new_markdown_cell
 from jupytext.compare import compare
 import jupytext