Url_for missing out parameters?

Having a bit of an issue with url_for

The current page I’m on has a named route as follows:

map.some_page ‘page/:id/:range’, :action => ‘the_action’

All looks fairly normal. I have an url_for on this page to make a link
to another page as so:

url_for(:controller=>‘other’, :action=>‘display’, :id=>5,
:range=>‘the_range’)

This URL comes out as:

/other/display/5

You’ll note that the ‘range’ is missing.
Passing in anything else other than ‘range’ works fine.

IE:

url_for(:controller=>‘other’, :action=>‘display’, :id=>5,
:test=>‘something’, :range=>‘the_range’)

results in:

/other/display/5?test=something

Any ideas why it’s ignoring the ‘range’ param?

Removing the :range param on the named route for the current page (note,
not the page the url_for is pointing to) make it work, but then that
breaks the nice url in the current page!

I’m running edge on windows with ruby 1.8.2.

Thanks in advance.