Something in w3.org's CSS is breaking Deadweight

[aanand]

/Users/aanand/.rvm/gems/ruby-1.9.2-p136/gems/nokogiri-1.4.4/lib/nokogiri/xml/node.rb:158:in `evaluate': Invalid expression: //*[contains(concat(' ', @class, ' '), ' data ')]//tbody//tr(., #) (Nokogiri::XML::XPath::SyntaxError)
    from /Users/aanand/.rvm/gems/ruby-1.9.2-p136/gems/nokogiri-1.4.4/lib/nokogiri/xml/node.rb:158:in `block in xpath'
    from /Users/aanand/.rvm/gems/ruby-1.9.2-p136/gems/nokogiri-1.4.4/lib/nokogiri/xml/node.rb:150:in `map'
    from /Users/aanand/.rvm/gems/ruby-1.9.2-p136/gems/nokogiri-1.4.4/lib/nokogiri/xml/node.rb:150:in `xpath'
    from /Users/aanand/.rvm/gems/ruby-1.9.2-p136/gems/nokogiri-1.4.4/lib/nokogiri/xml/node.rb:111:in `search'
    from /Users/aanand/src/deadweight/lib/deadweight.rb:42:in `block in analyze'
    from /Users/aanand/src/deadweight/lib/deadweight.rb:39:in `collect'
    from /Users/aanand/src/deadweight/lib/deadweight.rb:39:in `analyze'
    from /Users/aanand/src/deadweight/lib/deadweight.rb:133:in `process!'
    from /Users/aanand/src/deadweight/lib/deadweight.rb:120:in `block in run'
    from /Users/aanand/src/deadweight/lib/deadweight.rb:97:in `each'
    from /Users/aanand/src/deadweight/lib/deadweight.rb:97:in `run'
    from /Users/aanand/src/deadweight/lib/deadweight/cli.rb:113:in `process'
    from /Users/aanand/src/deadweight/lib/deadweight/cli.rb:88:in `execute!'
    from /Users/aanand/src/deadweight/lib/deadweight/cli.rb:19:in `execute'
    from bin/deadweight:4:in `'

[crsven]

Looks like it's choking on nth-child here:

http://www.w3.org/2008/site/css/minimum-src.css, line 319:
.data tbody tr:nth-child(even) {background-color:#f8f8f8;}

More trace:
//[contains(concat(' ', @Class, ' '), ' data ')]//tbody//tr(., #Nokogiri::CSS::Node:0x1291048)
/usr/local/lib/ruby/gems/1.9.1/gems/nokogiri-1.5.0/lib/nokogiri/xml/node.rb:160:in `evaluate': Invalid expression: //[contains(concat(' ', @Class, ' '), ' data ')]//tbody//tr(., #Nokogiri::CSS::Node:0x1291048) (Nokogiri::XML::XPath::SyntaxError)

[powertoaster]

I am getting almost the exact same error:

tbody tr:nth-child(even) td, tbody tr.even td {
background: #e5ecf9;
}

/stylesheets/slides/global.css
found 12 selectors

/
html
body
{snip}

rake aborted!
Invalid expression: //tbody//tr(., #Nokogiri::CSS::Node:0x48d9620)//td

Rails 3.0.9