Problem with include_context and shared_examples_for

Gemfile

source :rubygems
gem 'rspec'

output

.F

Failures:

  1) Egg 
     Failure/Error: Egg.new.class.should == RSpec::Mocks::Mock
       expected: RSpec::Mocks::Mock
            got: Egg (using ==)
       Diff:
       @@ -1,2 +1,2 @@
       -RSpec::Mocks::Mock
       +Egg
       
     # ./spec/shared_example_bug_spec.rb:30:in `block (2 levels) in <top (required)>'

Finished in 0.00236 seconds
2 examples, 1 failure

Failed examples:

rspec ./spec/shared_example_bug_spec.rb:29 # Egg 

shared_example_bug_spec.rb

require File.expand_path('spec/spec_helper')

class Egg
end

shared_context "egg mocking" do
  before do
    Egg.stub(:new).and_return mock('egg')
  end
end

describe Egg do
  include_context 'egg mocking'

  specify do
    Egg.new.class.should == RSpec::Mocks::Mock
  end
end


shared_examples_for 'an egg mocker' do
  include_context 'egg mocking'
end


describe Egg do
  it_behaves_like 'an egg mocker'

  specify do
    Egg.new.class.should == RSpec::Mocks::Mock
  end
end