diff --git a/src/_zkapauthorizer/tests/test_lease_maintenance.py b/src/_zkapauthorizer/tests/test_lease_maintenance.py
index e79e7c40b3c91c4d97483c0129ea177c18a09129..4ac9c066f9dfb1364817cc08a1bac4e3844c38f4 100644
--- a/src/_zkapauthorizer/tests/test_lease_maintenance.py
+++ b/src/_zkapauthorizer/tests/test_lease_maintenance.py
@@ -642,7 +642,7 @@ class MaintainLeasesFromRootTests(TestCase):
                 except KeyError:
                     continue
                 else:
-                    expected.extend(stat.size for stat in shares.values())
+                    expected.append(list(stat.size for stat in shares.values()))
 
         # The visit order doesn't matter.
         expected.sort()