diff --git a/src/_zkapauthorizer/_storage_server.py b/src/_zkapauthorizer/_storage_server.py
index c6f2c30612c5023f284f48b2d6ce9c5e120a7b7f..4f9b370d656412ed1eff6c57f7c487c6c843ea82 100644
--- a/src/_zkapauthorizer/_storage_server.py
+++ b/src/_zkapauthorizer/_storage_server.py
@@ -31,7 +31,7 @@ from os.path import join
 from struct import calcsize, unpack
 
 try:
-    from typing import Generator, Iterable, Tuple, List, Dict, Optional
+    from typing import Dict, Generator, Iterable, List, Optional, Tuple
 except ImportError:
     pass
 
diff --git a/src/_zkapauthorizer/lease_maintenance.py b/src/_zkapauthorizer/lease_maintenance.py
index 2920a4bf56478c214089049ce736130f048e0386..dcbb1010dbd84ad86718bc1b21c161259744d1c8 100644
--- a/src/_zkapauthorizer/lease_maintenance.py
+++ b/src/_zkapauthorizer/lease_maintenance.py
@@ -41,8 +41,8 @@ from twisted.python.log import err
 from zope.interface import implementer
 
 from .controller import bracket
-from .model import ILeaseMaintenanceObserver
 from .foolscap import ShareStat
+from .model import ILeaseMaintenanceObserver
 
 SERVICE_NAME = u"lease maintenance service"
 
diff --git a/src/_zkapauthorizer/tests/test_storage_server.py b/src/_zkapauthorizer/tests/test_storage_server.py
index aeeb98fe5baf34ac8c8d69a6e32dfdc5567c573a..8c4f57b82a06624122f6fac78e15a8c3ff9f1c9a 100644
--- a/src/_zkapauthorizer/tests/test_storage_server.py
+++ b/src/_zkapauthorizer/tests/test_storage_server.py
@@ -21,11 +21,11 @@ from __future__ import absolute_import, division
 from random import shuffle
 from time import time
 
-from prometheus_client import CollectorRegistry, Histogram
 from challenge_bypass_ristretto import RandomToken, random_signing_key
 from foolscap.referenceable import LocalReferenceable
 from hypothesis import given, note
 from hypothesis.strategies import integers, just, lists, one_of, tuples
+from prometheus_client import CollectorRegistry, Histogram
 from testtools import TestCase, skip
 from testtools.matchers import AfterPreprocessing, Equals, MatchesAll
 from twisted.internet.task import Clock