diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 0c9dfcf7201a..c47c23387525 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -400,10 +400,10 @@ as room administrator and will contain a message explaining what happened. Users
 to the new room will have power level `-10` by default, and thus be unable to speak.
 
 If `block` is `true`, users will be prevented from joining the old room.
-This option can also be used to pre-emptively block a room, even if it's unknown
-to this homeserver. In this case, the room will be blocked, and no further action
-will be taken. If `block` is `false`, attempting to delete an unknown room is
-invalid and will be rejected as a bad request.
+This option can in [Version 1](#version-1-old-version) also be used to pre-emptively
+block a room, even if it's unknown to this homeserver. In this case, the room will be
+blocked, and no further action will be taken. If `block` is `false`, attempting to
+delete an unknown room is invalid and will be rejected as a bad request.
 
 This API will remove all trace of the old room from your database after removing
 all local users. If `purge` is `true` (the default), all traces of the old room will
@@ -519,7 +519,8 @@ The following JSON body parameters are available:
                is not permitted and rooms in violation will be blocked.`
 * `block` - Optional. If set to `true`, this room will be added to a blocking list,
             preventing future attempts to join the room. Rooms can be blocked
-            even if they're not yet known to the homeserver. Defaults to `false`.
+            even if they're not yet known to the homeserver (only with
+            [Version 1](#version-1-old-version) of the API). Defaults to `false`.
 * `purge` - Optional. If set to `true`, it will remove all traces of the room from your database.
             Defaults to `true`.
 * `force_purge` - Optional, and ignored unless `purge` is `true`. If set to `true`, it
diff --git a/synapse/rest/admin/rooms.py b/synapse/rest/admin/rooms.py
index 05fc192eb780..2eecd39d6f04 100644
--- a/synapse/rest/admin/rooms.py
+++ b/synapse/rest/admin/rooms.py
@@ -153,7 +153,7 @@ async def on_GET(
                         **purge.asdict(),
                     }
                 ]
-        return 200, {"results": response}
+        return 200, {"results": cast(JsonDict, response)}
 
 
 class DeleteRoomStatusByPurgeIdRestServlet(RestServlet):
@@ -175,7 +175,7 @@ async def on_GET(
         if purge_status is None:
             raise NotFoundError("purge id '%s' not found" % purge_id)
 
-        return 200, purge_status.asdict()
+        return 200, cast(JsonDict, purge_status.asdict())
 
 
 class ListRoomRestServlet(RestServlet):
diff --git a/tests/rest/admin/test_room.py b/tests/rest/admin/test_room.py
index 2e23000af12a..4257066b9ff8 100644
--- a/tests/rest/admin/test_room.py
+++ b/tests/rest/admin/test_room.py
@@ -721,7 +721,9 @@ def test_delete_same_room_twice(self):
             access_token=self.admin_user_tok,
         )
 
-        self.assertEqual(HTTPStatus.BAD_REQUEST, second_channel.code, msg=second_channel.json_body)
+        self.assertEqual(
+            HTTPStatus.BAD_REQUEST, second_channel.code, msg=second_channel.json_body
+        )
         self.assertEqual(Codes.UNKNOWN, second_channel.json_body["errcode"])
         self.assertEqual(
             f"History purge already in progress for {self.room_id}",
@@ -1021,9 +1023,7 @@ def _test_result(
             access_token=self.admin_user_tok,
         )
         self.assertEqual(
-            HTTPStatus.OK,
-            channel_room_id.code,
-            msg=channel_room_id.json_body
+            HTTPStatus.OK, channel_room_id.code, msg=channel_room_id.json_body
         )
         self.assertEqual(1, len(channel_room_id.json_body["results"]))
         self.assertEqual(purge_id, channel_room_id.json_body["results"][0]["purge_id"])