diff --git a/swh/vault/in_memory_backend.py b/swh/vault/in_memory_backend.py
index ee79ba01dd5dde2f0641499ad4abcb1dcf5e78b8..74d6ee0af8a8a673c0282fd081dc7174ac445562 100644
--- a/swh/vault/in_memory_backend.py
+++ b/swh/vault/in_memory_backend.py
@@ -48,4 +48,4 @@ class InMemoryVaultBackend:
         raise NotImplementedError("InMemoryVaultBackend.batch_cook()")
 
     def batch_progress(self, batch_id: int) -> Dict[str, Any]:
-        pass
+        return {}
diff --git a/tox.ini b/tox.ini
index f6e3d2092727f57ce6609f680cb64cc15d3c5fb0..89358a5c54a8727cacc662d02d8c38d2d976d4c8 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,7 +35,7 @@ extras =
   testing
   graph
 deps =
-  mypy==0.942
+  mypy==1.0.1
 commands =
   mypy swh