The last commit on github was 12/07/2022 to make the library compatible with Ruby 3.2.2. But this commit is not in the gem 0.13.0 pushed on Rubygems.org at https://rubygems.org/gems/fiber-scheduler.

Therefore, the gem is creating errors on Ruby 3.2 - Expect 4 params, provided 3. on line 175 of fiber_scheduler.rb.

It took a while to figure it out. Hope this helps other people.