bundle install => using from system gems

I got an issue when running bundle install in a Rails3 app

I am using rvm and a specific gemset

rvm gemset list info: gemsets : for ruby-1.8.7-p248 (found in /Users/yves/.rvm/gems/) Rails3 global

rails --version Rails 3.0.0.beta4 ruby -v ruby 1.8.7 (2009-12-24 patchlevel 248) [i686-darwin10.4.0]

ok until there gem list

*** LOCAL GEMS *** abstract (1.0.0) actionmailer (3.0.0.beta4) actionpack (3.0.0.beta4) activemodel (3.0.0.beta4) activerecord (3.0.0.beta4) activeresource (3.0.0.beta4) activesupport (3.0.0.beta4) ...

ok until there my Gemfile seems ok too source 'http://rubygems.org' gem 'rails', '3.0.0.beta4' ...

but when running the command > bundle install I get all gems used from sustem gems Using rake (0.8.7) from system gems Using abstract (1.0.0) from system gems Using activesupport (3.0.0.beta4) from system gems Using builder (2.1.2) from system gems ....

and an error at the end Copying .gem files into vendor/cache   * rake-0.8.7.gem   * abstract-1.0.0.gem Missing gem file 'activesupport-3.0.0.beta4.gem'. Run `bundle install` to install missing gems. ...

why this file is missing ?