Rails 3 - bundle install : ffi 0.5.4 gem error - building with native extensions

kristian-mandrups-macbook-pro:demo_app kristianconsult$ bundle install
Updating git://github.com/rails/rails.git
Updating git://github.com/rails/arel.git
Updating git://github.com/rails/rack.git
Updating git://github.com/rspec/rspec.git
Updating git://github.com/negonicrac/rspec-rails.git
Updating git://github.com/kristianmandrup/cucumber-rails.git
Fetching source index from http://gemcutter.org
Fetching source index from http://gems.github.com
Resolving dependencies
Installing abstract (1.0.0) from .gem files at /Users/kristianconsult/
my_rails/rails3_apps/demo_app/vendor/cache
Installing actionmailer (3.0.0.beta1) from git://github.com/rails/rails.git
(at master)
...
Installing ffi (0.5.4) from .gem files at /Users/kristianconsult/
my_rails/rails3_apps/demo_app/vendor/cache with native extensions /usr/
local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/rubygems/
installer.rb:504:in `rescue in block in build_extensions': ERROR:
Failed to build gem native extension.
(Gem::Installer::ExtensionBuildError)

rake RUBYARCHDIR=/Users/kristianconsult/my_rails/rails3_apps/demo_app/
vendor/gems/ffi-0.5.4/lib RUBYLIBDIR=/Users/kristianconsult/my_rails/
rails3_apps/demo_app/vendor/gems/ffi-0.5.4/lib
/usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/rubygems.rb:
827:in `report_activate_error': Could not find RubyGem rake (>= 0)
(Gem::LoadError)
  from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/
rubygems.rb:261:in `activate'
  from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/
rubygems.rb:68:in `gem'
  from <internal:gem_prelude>:273:in `push_gem_version_on_load_path'
  from <internal:gem_prelude>:14:in `gem'
  from /usr/local/bin/rake:18:in `<main>'

Gem files will remain installed in /Users/kristianconsult/my_rails/
rails3_apps/demo_app/vendor/gems/ffi-0.5.4 for inspection.
Results logged to /Users/kristianconsult/my_rails/rails3_apps/demo_app/
vendor/gems/ffi-0.5.4/gen/gem_make.out
  from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/
rubygems/installer.rb:507:in `block in build_extensions'
  from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/
rubygems/installer.rb:467:in `each'
  from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/
rubygems/installer.rb:467:in `build_extensions'
  from /usr/local/Cellar/ruby/1.9.1-p378/lib/ruby/site_ruby/1.9.1/
rubygems/installer.rb:219:in `install'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/source.rb:127:in `install'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/installer.rb:25:in `block in run'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/installer.rb:15:in `each'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/installer.rb:15:in `run'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/installer.rb:6:in `install'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/cli.rb:54:in `install'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/vendor/thor/task.rb:32:in `run'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/vendor/thor/invocation.rb:108:in `block in invoke'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/vendor/thor/invocation.rb:115:in `call'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/vendor/thor/invocation.rb:115:in `invoke'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/vendor/thor.rb:137:in `block in start'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/vendor/thor/base.rb:369:in `start'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/lib/
bundler/vendor/thor.rb:124:in `start'
  from /Users/kristianconsult/.gem/ruby/1.9.1/gems/bundler-0.9.3/bin/
bundle:4:in `<top (required)>'
  from /Users/kristianconsult/.gem/ruby/1.9.1/bin/bundle:19:in `load'
  from /Users/kristianconsult/.gem/ruby/1.9.1/bin/bundle:19:in `<main>'