diff --git a/src/borg/testsuite/legacy_archives_test.py b/src/borg/testsuite/legacy_archives_test.py
index 4e7d70880..55e418095 100644
--- a/src/borg/testsuite/legacy_archives_test.py
+++ b/src/borg/testsuite/legacy_archives_test.py
@@ -461,7 +461,7 @@ def test_legacy_archives_satisfies_archives_interface():
 
 class _FakeLegacyRepo(LegacyRepository):
     def __init__(self):
-        pass
+        self.lock = None
 
 
 def test_manifest_creates_legacy_archives_for_legacy_repo():