auto_link does not add attributes to hrefs like the docs describe

This is only a problem with the "new" API for auto_link, the old API works fine. An example from the console:

$ script/console
Loading development environment (Rails 2.3.4)
>> include ActionView::Helpers::TextHelper
=> Object
>> include ActionView::Helpers::TagHelper
=> Object

# The docs say this should work:
>> auto_link("http://google.com", :href_options => { :target => "_blank" })
=> "<a href=\"http://google.com\">http://google.com</a>"

# This works:
>> auto_link("http://google.com", :urls, :target => "_blank")
=> "<a href=\"http://google.com\" target=\"_blank\">http://google.com</a>"