Url_for - results inconsistency?

Hi all,

I recently noticed something really weird in url_for results
let’s say that we have something like this somewhere in code

URL1:<%=url_for( {:action=>'foobar'}.merge({'action'=>'ohmy'}) )%>
URL2:<%=url_for( {'action'=>'ohmy'}.merge({:action=>'foobar'}) )%>

and then please consider following two cases…

case 1. webrick, ruby 1.8.4, rails 1.0
result:
URL1:…/foobar
URL2:…/foobar

case 2: lighttpd-1.4.11, ruby 1.8.4, rails 1.0
result:
URL1:…/ohmy
URL2:…/ohmy

What is the cause of such behavior, and is there any way to avoid this
kind of inconsistency ?
Can this be treated as a bug ?

–l00pek