diff --git a/swh/storage/tests/storage_testing.py b/swh/storage/tests/storage_testing.py
--- a/swh/storage/tests/storage_testing.py
+++ b/swh/storage/tests/storage_testing.py
@@ -55,6 +55,7 @@
 
     def tearDown(self):
         self.objtmp.cleanup()
+        self.storage = None
         super().tearDown()
 
     def reset_storage_tables(self):