406 on POST application/xml with Content-Length: 0

When POSTing with Content-Type: application/xml and Content-Length: 0,
Services always returns the following error:

406 Not Acceptable:

The POST works with no Content-Type set or when set to application/json.
The error prevents the use of AngularJS $resource with Drupal REST endpoints that utilize POST with no content because AngularJS always sets the Content-Type header to application/xml.

It looks to me like RESTServer::parseXML is throwing an exception on processing NULL content, but I'm new to this stuff so I could be wrong.

Here's a capture of the HTTP conversation:

POST /rest/user/logout.json HTTP/1.1
Host: example.com
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.8; rv:17.0) Gecko/20100101 Firefox/17.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Cookie: cookie-here
Content-Type: application/xml
Cache-Control: max-age=0, no-cache
Pragma: no-cache
Content-Length: 0

HTTP/1.1 406 Not Acceptable:
Date: Thu, 13 Dec 2012 02:28:42 GMT
Server: Apache
Expires: Sun, 19 Nov 1978 05:00:00 GMT
Cache-Control: no-cache, must-revalidate, post-check=0, pre-check=0
ETag: "1355365722"
Last-Modified: Thu, 13 Dec 2012 02:28:42 GMT
Access-Control-Allow-Origin: http://localhost:8000
Access-Control-Allow-Headers: X-Requested-With, Content-Type
Access-Control-Allow-Methods: GET, HEAD, POST, PUT
Access-Control-Max-Age: 1728000
Vary: Accept-Encoding
Content-Encoding: gzip
Content-Length: 20
Keep-Alive: timeout=2, max=100
Connection: Keep-Alive
Content-Type: text/html

It's also worth noting that the error message ("406 Not Acceptable:") seems cut off and is a little uninformative.