diff --git a/lib/mastodon/redis_configuration.rb b/lib/mastodon/redis_configuration.rb
index 93d35391c4ee00..4cc3e8ccde9667 100644
--- a/lib/mastodon/redis_configuration.rb
+++ b/lib/mastodon/redis_configuration.rb
@@ -21,7 +21,7 @@ def cache
                  expires_in: 10.minutes,
                  connect_timeout: 5,
                  pool: {
-                   size: Sidekiq.server? ? Sidekiq[:concurrency] : Integer(ENV['MAX_THREADS'] || 5),
+                   size: Sidekiq.server? ? Sidekiq.default_configuration.concurrency : Integer(ENV['MAX_THREADS'] || 5),
                    timeout: 5,
                  },
                })