diff --git a/tests/test_utils_snapshot.py b/tests/test_utils_snapshot.py
index 460b7449..dc6b59fb 100644
--- a/tests/test_utils_snapshot.py
+++ b/tests/test_utils_snapshot.py
@@ -25,8 +25,8 @@ class FakeAdjustable(Adjustable):
         return value
 
 @pytest.fixture(autouse=True)
-def clean_registry():
-    instances.cache_clear()
+def clean_registry(monkeypatch):
+    monkeypatch.setattr('slic.utils.registry.instances', lambda _: [])
 
 def test_snapshot_excludes_internal_by_default():
     visible = FakeAdjustable("vis_id", "visible", False)