gem version conflict on master branch

Fixed http://github.com/rails/arel/commit/832186036c5eb825de23e5d19ea3b56...

Created a brand new rails app. And this is what I have in my Gemfile.

source 'http://rubygems.org'

#gem 'rails', '3.0.0'
gem 'rails', :git => 'git://github.com/rails/rails.git'

$ bundle install
Updating git://github.com/rails/rails.git
Fetching source index for http://rubygems.org/
Bundler could not find compatible versions for gem "activesupport":
  In Gemfile:
    rails depends on
      activesupport (~> 3.0.0)

    rails depends on
      activesupport (3.1.0.beta)

$ gem list bundler

*** LOCAL GEMS ***

bundler (1.0.0, 1.0.0.rc.6, 1.0.0.rc.4, 1.0.0.rc.2, 1.0.0.rc.1, 1.0.0.beta.9, 1.0.0.beta.5, 1.0.0.beta.4, 0.9.26)

Surprisingly on a clone of rails bundle install works fine. I am getting this error only when I have an app using rails master.

This is generating the app with --dev only. You should add gem 'arel', :git => 'git://github.com/rails/arel.git'