This works fine:

$ rake cucumber:all

$ script/plugin install git://github.com/bmabey/email-spec.git
remote: Counting objects: 162, done.
remote: Compressing objects: 100% (130/130), done.
remote: Total 162 (delta 18), reused 79 (delta 13)
Receiving objects: 100% (162/162), 127.65 KiB | 15 KiB/s, done.
Resolving deltas: 100% (18/18), done.
From git://github.com/bmabey/email-spec
 * branch            HEAD       -> FETCH_HEAD

$ script/generate email_spec
      exists  features/step_definitions
      create  features/step_definitions/email_steps.rb

And I add 'require 'email_spec/cucumber' in

/feature/support/env.rb

so it looks somethinng like:

 require File.expand_path(File.dirname(__FILE__) + '/../../config/environment')
 require 'cucumber/rails/world'
 require 'cucumber/formatter/unicode' # Comment out this line if you don't want Cucumber  Unicode support
 require 'email_spec/cucumber'

and now:

rake cucumber:all

gives me this error:

$ rake cucumber:all --trace
(in /Users/leonardodarioperna/Projects/frestyl/frestyl)
** Invoke cucumber:all (first_time)
** Invoke cucumber:ok (first_time)
** Invoke db:test:prepare (first_time)
** Invoke db:abort_if_pending_migrations (first_time)
** Invoke environment (first_time)
** Execute environment
** Execute db:abort_if_pending_migrations
** Execute db:test:prepare
** Invoke db:test:load (first_time)
** Invoke db:test:purge (first_time)
** Invoke environment 
** Execute db:test:purge
** Execute db:test:load
** Invoke db:schema:load (first_time)
** Invoke environment 
** Execute db:schema:load
** Execute cucumber:ok
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/bin/ruby -I "/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/lib:lib" "/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/bin/cucumber"  --profile default
cucumber.yml was not found.  Please refer to cucumber's documentation on defining profiles in cucumber.yml.  You must define a 'default' profile to use the cucumber command without any arguments.
Type 'cucumber --help' for usage.
rake aborted!
Command failed with status (1): [/System/Library/Frameworks/Ruby.framework/...]
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:995:in `sh'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1010:in `call'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1010:in `sh'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1094:in `sh'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1029:in `ruby'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1094:in `ruby'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/lib/cucumber/rake/task.rb:68:in `run'
/Library/Ruby/Gems/1.8/gems/cucumber-0.4.4/lib/cucumber/rake/task.rb:138:in `define_task'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `call'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:636:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:631:in `execute'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:597:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:607:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:604:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:604:in `invoke_prerequisites'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:596:in `invoke_with_call_chain'
/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/monitor.rb:242:in `synchronize'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:590:in `invoke_with_call_chain'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:583:in `invoke'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2051:in `invoke_task'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `each'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2029:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2023:in `top_level'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2001:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:2068:in `standard_exception_handling'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/lib/rake.rb:1998:in `run'
/Library/Ruby/Gems/1.8/gems/rake-0.8.7/bin/rake:31
/usr/bin/rake:19:in `load'
/usr/bin/rake:19

WHY?

but the command:

$ cucumber

still works

Any idea?