Can you adjust the size of the Rails Geocoder Redis cache?

We have a Rails app deployed in Heroku using Rails Geocoding with a Redis cache. I assume entries are cached to fill some percent of the memory and I recall it running around 90%, but the Redis usage has grown recently.

We have a 1 GB plan and stats show 1,023.65 MB memory used and we are getting an error in Redis now:

OOM command not allowed when used memory > 'maxmemory

We are using Redis for Sidekiq so it's possible that has been using more space, but how do I fix this issue? Can I limit the size of the Geocoder cache?