Could not find the constant in class_eval.

test_include.rb

module A
  B = 10
  def f
    class_eval { B }
  end
end

class K
  extend A
  f
end

__END__

$ macruby test_include.rb
test_include.rb:4:in `f': uninitialized constant K::B (NameError)
        from test_include.rb:10:in `block'
        from test_include.rb:8:in `<main>'