Rails 5.2 + Sidekiq 6: You are connecting to Redis v3.2.6, Sidekiq requires Redis v4.0.0 or greater

I was updating my Rails app to 5.2.x along with Sidekiq and Redis. The Redis version is

bundle show redis
/Users/adam/.rvm/gems/ruby-2.6.3/gems/redis-4.1.3

When I try to run Sidekiq locally (running on OSX), I get this error message (You are connecting to Redis v3.2.6, Sidekiq requires Redis v4.0.0 or greater):

2020-03-22T08:44:03.521Z pid=55312 tid=owg9hjbz0 INFO: Booting Sidekiq 6.0.5 with redis options {:url=>"redis://127.0.0.1:6379", :namespace=>"sidekiq_myapp_com_development", :id=>"Sidekiq-server-PID-55312"}
2020-03-22T08:44:04.851Z pid=55312 tid=owg9hjbz0 INFO: Booted Rails 5.2.4.2 application in development environment
2020-03-22T08:44:04.852Z pid=55312 tid=owg9hjbz0 INFO: Running in ruby 2.6.3p62 (2019-04-16 revision 67580) [x86_64-darwin19]
2020-03-22T08:44:04.853Z pid=55312 tid=owg9hjbz0 INFO: See LICENSE and the LGPL-3.0 for licensing details.
2020-03-22T08:44:04.853Z pid=55312 tid=owg9hjbz0 INFO: Upgrade to Sidekiq Pro for more features and support: http://sidekiq.org
You are connecting to Redis v3.2.6, Sidekiq requires Redis v4.0.0 or greater
/Users/adam/.rvm/gems/ruby-2.6.3/gems/sidekiq-6.0.5/lib/sidekiq/cli.rb:62:in `run'
/Users/adam/.rvm/gems/ruby-2.6.3/gems/sidekiq-6.0.5/bin/sidekiq:12:in `<top (required)>'
/Users/adam/.rvm/gems/ruby-2.6.3/bin/sidekiq:23:in `load'
/Users/adam/.rvm/gems/ruby-2.6.3/bin/sidekiq:23:in `<main>'
/Users/adam/.rvm/gems/ruby-2.6.3/bin/ruby_executable_hooks:24:in `eval'
/Users/adam/.rvm/gems/ruby-2.6.3/bin/ruby_executable_hooks:24:in `<main>'

If I check redis-server --version:

Redis server v=3.2.6 sha=00000000:0 malloc=libc bits=64 build=cd15ebf62a9a5bbe

Where do I set the correct (4.x) version for Redis?

I also checked the app on the server (Ubuntu on EC2) after deploying and there's the same problem.