Missing </head> in source of CSS specs causing problems for htmldiff tool?

If you look at the HTML source code of a CSS specification (e.g.
http://www.w3.org/TR/css3-flexbox/), you'll notice that the </head> tag is
missing. This appears to cause problems with the htmldiff tool [1],
specifically with its text highlighting functionality. (See this Twitter
thread [2] for details.)

For comparison, this is how the output of the htmldiff tool looks like with
text highlighting [3], and this is how it looks without [4].

I don't know how the HTML source code for the CSS WG specs is generated,
but if there exists one master template, please consider adding the </head>
tag to it.

[1]: http://services.w3.org/htmldiff
[2]: https://twitter.com/simevidas/status/331406266209562624
[3]:
http://services.w3.org/htmldiff?doc1=http://www.w3.org/TR/2012/WD-tracking-dnt-20121002/&doc2=http://www.w3.org/TR/2013/WD-tracking-dnt-20130430/
[4]:
http://services.w3.org/htmldiff?doc1=http://www.w3.org/TR/2012/WD-selectors4-20120823/&doc2=http://www.w3.org/TR/2013/WD-selectors4-20130502/

-- @simevidas