render :text => Proc

As described at http://pastie.org/455603

Using render :text with a Proc causes unusual errors

class FoosController < ApplicationController
  def bar
    render :text => lambda { |response, output|
      Foo.new.inspect
      output.write "Blah"
    }
  end
end

Line 4 generates the error "Read error: #<ArgumentError: A copy of FoosController has been removed from the module tree but is still active!>". If I remove line 4, or place it outside the lambda, no error occurs and "Blah" is successfully output