No, I think the current code is calling ```defer_cleanup``` on the ```RateControllingUrlAsyncFetcher```, not the ```SerfUrlAsyncFetcher```. See above on line 163 where ```fetcher``` is assigned to the ```RateControllingUrlAsyncFetcher```. I think all that needs to happen is change ```fetcher``` on line 172 (the ```defer_cleanup``` call) to ```serf_fetcher```, and remove the ```static_cast``` (which is also a red flag).