Is System.Net.FileWebResponse class so limited WRT to content type?

I got a problem. It's .NET problem. In XInclude.NET I'm fetching resources by URI using WebRequest/WebResponse classes. Everything seems to be working fine, the only problem is as follows: when the URI is file system URI, the content type property is always "application/octet-stream". Looks like it's hardcoded in System.Net.FileWebResponse class (sic!). I mean - when I open Windows Explorer the file's properties are: "Type of the file: XML File" and "Opens with: XMLSPY". So the Windows definitely knows it's XML and in the registry I can see .xml file extension is associated with "text/xml" content type, so why FileWebResponse always says "application/octet-stream"? Am I doing something wrong or it's soo limited in that matter? Any workarounds?