How do I resolve this error that keeps me from starting rails server?

Hey guys I have searched documentation to this error that I have never seen before in working with Ruby on Rails. I just got a new MacBook and I installed Rails 4.2 and Ruby 2.4 and when I attempt to run rails server, I get this error:

.rbenv/versions/2.4.0/lib/ruby/gems/2.4.0/gems/thread_safe-0.3.5/lib/thread_safe/cache.rb:155: warning: constant ::Fixnum is deprecated

How do I eliminate this error that is keeping me from starting up the rails server?