REXML::Document.new() raises REXML::ParseException

[Agt]

REXML::Document.new doesn't accept "<a x:foo='1' y:foo='2'/>" for some reason :(

$ irb
irb(main):001:0> require 'rexml/document'
=> true
irb(main):002:0> REXML::Document.new "<a foo='3' x:foo='1'
y:foo='2'/>"
=> <UNDEFINED> ... </>
irb(main):003:0> REXML::Document.new "<a foo='3'/>"
=> <UNDEFINED> ... </>
irb(main):004:0> REXML::Document.new "<a x:foo='1' y:foo='2'/>"
REXML::ParseException: #<REXML::ParseException: Namespace
conflict in adding attribute "foo": Prefix "x" = "" and prefix "y" = "">
/usr/local/lib/ruby/1.8/rexml/element.rb:1094:in `[]='
/usr/local/lib/ruby/1.8/rexml/element.rb:280:in `add_element'
/usr/local/lib/ruby/1.8/rexml/element.rb:279:in `each'
/usr/local/lib/ruby/1.8/rexml/element.rb:279:in `add_element'
/usr/local/lib/ruby/1.8/rexml/document.rb:88:in `add_element'
/usr/local/lib/ruby/1.8/rexml/parsers/treeparser.rb:28:in `parse'
/usr/local/lib/ruby/1.8/rexml/document.rb:176:in `build'
/usr/local/lib/ruby/1.8/rexml/document.rb:45:in `initialize'
(irb):4:in `new'
(irb):4:in `irb_binding'
/usr/local/lib/ruby/1.8/irb/workspace.rb:52:in `irb_binding'
/usr/local/lib/ruby/1.8/irb/workspace.rb:52
...
Namespace conflict in adding attribute "foo": Prefix "x" =
"" and prefix "y" = "
"
Line: 
Position: 
Last 80 unconsumed characters:

        from
/usr/local/lib/ruby/1.8/rexml/parsers/treeparser.rb:85:in `parse'
        from
/usr/local/lib/ruby/1.8/rexml/document.rb:176:in `build'
        from /usr/local/lib/ruby/1.8/rexml/document.rb:45:in `initialize'
        from (irb):4:in `new'
        from (irb):4

[ser]

The example XML is malformed, and REXML is correct in throwing an exception. It would be preferable if REXML threw an "undeclared namespace" exception, because this is the real reason the XML is malformed; instead, it is assuming both the "x" and "y" prefixes point to the empty namespace "", and it is invalid XML to specify two attributes of the same tag with the same name and namespace.