Error While creating a new Rails Project in Rails 5.0.0.rc1

I am trying to create a new Rails project- in fact, it is chapter 3 of Michael Hartl RubyonRails. Anytime I try to create the sample_app I get this message :

$ rails 5.0.0.rc1 new sample_app
/usr/local/rvm/rubies/ruby-2.3.0/lib/ruby/2.3.0/rubygems/dependency.rb:319:in to_specs': Could not find 'railties' (= 5.0.0.rc1) - did find: [railties-4.2.2] (Gem::LoadError) Checked in 'GEM_PATH=/usr/local/rvm/gems/ruby-2.3.0:/usr/local/rvm/gems/ruby-2.3.0@global', executegem env` for more information

It looks like for some reason it is not adding the new app gems. I am a total newbie, so I appreciate any input in trying to figure this stuff out !

Thanks a lot !

J