diff --git a/hathor/event/websocket/request.py b/hathor/event/websocket/request.py
index c4c5efd04..446c62840 100644
--- a/hathor/event/websocket/request.py
+++ b/hathor/event/websocket/request.py
@@ -12,9 +12,9 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Literal, Optional, Union
+from typing import Annotated, Literal, Optional, Union
 
-from pydantic import NonNegativeInt
+from pydantic import Field, NonNegativeInt
 
 from hathor.utils.pydantic import BaseModel
 
@@ -54,9 +54,7 @@ class StopStreamRequest(BaseModel):
     type: Literal['STOP_STREAM']
 
 
-# This could be more performatic in Python 3.9:
-# Request = Annotated[StartStreamRequest | AckRequest | StopStreamRequest, Field(discriminator='type')]
-Request = Union[StartStreamRequest, AckRequest, StopStreamRequest]
+Request = Annotated[Union[StartStreamRequest, AckRequest, StopStreamRequest], Field(discriminator='type')]
 
 
 class RequestWrapper(BaseModel):
diff --git a/hathor/indexes/rocksdb_utils.py b/hathor/indexes/rocksdb_utils.py
index ad1a94325..3a98fed2d 100644
--- a/hathor/indexes/rocksdb_utils.py
+++ b/hathor/indexes/rocksdb_utils.py
@@ -121,8 +121,7 @@ def _clone_into_dict(self) -> Dict[bytes, bytes]:
         return {k: v for (_, k), v in it}
 
 
-# XXX: should be `Collection[bytes]`, which only works on Python 3.9+
-class RocksDBSimpleSet(Collection, RocksDBIndexUtils):
+class RocksDBSimpleSet(Collection[bytes], RocksDBIndexUtils):
     def __init__(self, db: 'rocksdb.DB', log: 'structlog.stdlib.BoundLogger', *, cf_name: bytes) -> None:
         self.log = log
         super().__init__(db, cf_name)