X-Frame-Options ALLOW-FROM a specific site allows from all
===

I'm using a rails application to serve a page from abc.com. In it, I set the response headers in my application controller (for every request through before_filter) so that it can be accessed through an iframe only from a specific site (xyz.com), through the following code:

    def set_x_frame_options
      response.headers["X-Frame-Options"] = "ALLOW-FROM http://www.xyz.com"
    end

The problem is that, not only I'm able to access the page from abc.com on xyz but also on any other website. I want to limit the access to only xyz.com. When I examine the response headers in chrome console I can see the X-Frame-Options is being passed on correctly. This is happening across all browsers. Am I missing something?