[XHTML 2] ismap attribute URI creation

Dear HTML Working Group,

"The user agent derives a new URI from the URI specified by the href 
attribute of the element, by appending a '?' followed by the x and y 
coordinates, seperated by a comma."

What happens if the href already contains a ?
ie
<p href="http://www.example.com/cgi-bin/map?chickens"
      src="map.png" ismap="ismap">
   Our location.
</p>

Please clarify this so the result is not
http://www.example.com/cgi-bin/map?chickens?1,1

Regards,

Jim Ley