diff --git a/src/_zkapauthorizer/_storage_server.py b/src/_zkapauthorizer/_storage_server.py
index 97c500e48f7cfa33844741564d3b114d7fc6528f..f737e741eff646af375df8fb18c949e545cb24d7 100644
--- a/src/_zkapauthorizer/_storage_server.py
+++ b/src/_zkapauthorizer/_storage_server.py
@@ -34,8 +34,8 @@ import attr
 from allmydata.interfaces import RIStorageServer
 from allmydata.storage.common import storage_index_to_dir
 from allmydata.storage.immutable import ShareFile
-from allmydata.storage.mutable import MutableShareFile
 from allmydata.storage.lease import LeaseInfo
+from allmydata.storage.mutable import MutableShareFile
 from allmydata.storage.shares import get_share_file
 from allmydata.util.base32 import b2a
 from attr.validators import instance_of, provides