diff --git a/radicale/app/__init__.py b/radicale/app/__init__.py
index bb46b3c..2f87efa 100644
--- a/radicale/app/__init__.py
+++ b/radicale/app/__init__.py
@@ -29,7 +29,6 @@ import datetime
 import io
 import logging
 import pkg_resources
-import posixpath
 import pprint
 import random
 import time
@@ -52,6 +51,8 @@ from radicale.app.put import ApplicationPutMixin
 from radicale.app.report import ApplicationReportMixin
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 VERSION = pkg_resources.get_distribution("radicale").version
 
 
diff --git a/radicale/app/get.py b/radicale/app/get.py
index 7b58a8b..71e4d51 100644
--- a/radicale/app/get.py
+++ b/radicale/app/get.py
@@ -17,13 +17,14 @@
 # You should have received a copy of the GNU General Public License
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
-import posixpath
 from http import client
 from urllib.parse import quote
 
 from radicale import httputils, pathutils, storage, xmlutils
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 def propose_filename(collection):
     """Propose a filename for a collection."""
diff --git a/radicale/app/mkcalendar.py b/radicale/app/mkcalendar.py
index 42de870..a0b0048 100644
--- a/radicale/app/mkcalendar.py
+++ b/radicale/app/mkcalendar.py
@@ -17,7 +17,6 @@
 # You should have received a copy of the GNU General Public License
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
-import posixpath
 import socket
 from http import client
 
@@ -26,6 +25,8 @@ from radicale import item as radicale_item
 from radicale import pathutils, storage, xmlutils
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 class ApplicationMkcalendarMixin:
     def do_MKCALENDAR(self, environ, base_prefix, path, user):
diff --git a/radicale/app/mkcol.py b/radicale/app/mkcol.py
index 43e3945..0a7cdd4 100644
--- a/radicale/app/mkcol.py
+++ b/radicale/app/mkcol.py
@@ -17,7 +17,6 @@
 # You should have received a copy of the GNU General Public License
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
-import posixpath
 import socket
 from http import client
 
@@ -26,6 +25,8 @@ from radicale import item as radicale_item
 from radicale import pathutils, storage, xmlutils
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 class ApplicationMkcolMixin:
     def do_MKCOL(self, environ, base_prefix, path, user):
diff --git a/radicale/app/move.py b/radicale/app/move.py
index 79155b5..3e20df1 100644
--- a/radicale/app/move.py
+++ b/radicale/app/move.py
@@ -17,13 +17,14 @@
 # You should have received a copy of the GNU General Public License
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
-import posixpath
 from http import client
 from urllib.parse import urlparse
 
 from radicale import httputils, pathutils, storage
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 class ApplicationMoveMixin:
     def do_MOVE(self, environ, base_prefix, path, user):
diff --git a/radicale/app/propfind.py b/radicale/app/propfind.py
index f7bec9d..770772f 100644
--- a/radicale/app/propfind.py
+++ b/radicale/app/propfind.py
@@ -18,7 +18,6 @@
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
 import itertools
-import posixpath
 import socket
 from http import client
 from xml.etree import ElementTree as ET
@@ -26,6 +25,8 @@ from xml.etree import ElementTree as ET
 from radicale import httputils, pathutils, rights, storage, xmlutils
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 def xml_propfind(base_prefix, path, xml_request, allowed_items, user):
     """Read and answer PROPFIND requests.
diff --git a/radicale/app/put.py b/radicale/app/put.py
index 2938a25..25bad32 100644
--- a/radicale/app/put.py
+++ b/radicale/app/put.py
@@ -18,7 +18,6 @@
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
 import itertools
-import posixpath
 import socket
 import sys
 from http import client
@@ -30,6 +29,8 @@ from radicale import item as radicale_item
 from radicale import pathutils, storage, xmlutils
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 class ApplicationPutMixin:
     def do_PUT(self, environ, base_prefix, path, user):
diff --git a/radicale/app/report.py b/radicale/app/report.py
index b6f6745..1f6abc8 100644
--- a/radicale/app/report.py
+++ b/radicale/app/report.py
@@ -18,7 +18,6 @@
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
 import contextlib
-import posixpath
 import socket
 from http import client
 from urllib.parse import unquote, urlparse
@@ -28,6 +27,8 @@ from radicale import httputils, pathutils, storage, xmlutils
 from radicale.item import filter as radicale_filter
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 def xml_report(base_prefix, path, xml_request, collection, unlock_storage_fn):
     """Read and answer REPORT requests.
diff --git a/radicale/pathutils.py b/radicale/pathutils.py
index 5faaa90..eee3e6d 100644
--- a/radicale/pathutils.py
+++ b/radicale/pathutils.py
@@ -18,9 +18,10 @@
 
 import contextlib
 import os
-import posixpath
 import threading
 
+import posixpath  # isort:skip
+
 if os.name == "nt":
     import ctypes
     import ctypes.wintypes
diff --git a/radicale/storage/multifilesystem/discover.py b/radicale/storage/multifilesystem/discover.py
index e2992bf..f41cf35 100644
--- a/radicale/storage/multifilesystem/discover.py
+++ b/radicale/storage/multifilesystem/discover.py
@@ -18,11 +18,12 @@
 
 import contextlib
 import os
-import posixpath
 
 from radicale import pathutils
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 
 class CollectionDiscoverMixin:
     @classmethod
diff --git a/radicale/tests/test_auth.py b/radicale/tests/test_auth.py
index 521e5d5..4aae5b7 100644
--- a/radicale/tests/test_auth.py
+++ b/radicale/tests/test_auth.py
@@ -26,12 +26,12 @@ import os
 import shutil
 import tempfile
 
-import pytest
-
 from radicale import Application, config
 
 from .test_base import BaseTest
 
+import pytest  # isort:skip
+
 
 class TestBaseAuthRequests(BaseTest):
     """Tests basic requests with auth.
diff --git a/radicale/tests/test_base.py b/radicale/tests/test_base.py
index 7749732..996a0f7 100644
--- a/radicale/tests/test_base.py
+++ b/radicale/tests/test_base.py
@@ -22,20 +22,21 @@ Radicale tests with simple requests.
 
 import base64
 import os
-import posixpath
 import shutil
 import sys
 import tempfile
 import xml.etree.ElementTree as ET
 from functools import partial
 
-import pytest
-
 from radicale import Application, config
 
 from . import BaseTest
 from .helpers import get_file_content
 
+import posixpath  # isort:skip
+
+import pytest  # isort:skip
+
 
 class BaseRequestsMixIn:
     """Tests with simple requests."""
diff --git a/radicale/web/internal.py b/radicale/web/internal.py
index 7c9fa4a..de8b6ed 100644
--- a/radicale/web/internal.py
+++ b/radicale/web/internal.py
@@ -15,7 +15,6 @@
 # along with Radicale.  If not, see <http://www.gnu.org/licenses/>.
 
 import os
-import posixpath
 import time
 from http import client
 
@@ -24,6 +23,8 @@ import pkg_resources
 from radicale import httputils, pathutils, web
 from radicale.log import logger
 
+import posixpath  # isort:skip
+
 MIMETYPES = {
     ".css": "text/css",
     ".eot": "application/vnd.ms-fontobject",