C# - Getting Log4net's XML Configuration File Read In Webforms?

I'm trying to get log4net working in a 'classic' webforms app, using a log4net XML configuration file that I know is correct, as it is a copy of a file I use successfully with a number of other applications. I have the config.log4net file in the main site folder (C:inetpubwwwroot), and I configure log4net in Global.asax.cs as follows:

protected void Application_Start(Object sender, EventArgs e)
{
var log = LogManager.GetLogger("SomeWebsite");
XmlConfigurator.Configure(new FileInfo("config.log4net"));
// bind log to the DI container
...
}

Whenever I then use the log instance (even within Application_Start) nothing happens, not even an error. I know that if config.log4net is misconfigured, log4net will silently fail, but I am sure that this isn't the problem. I have a feeling it has to do with FileInfo's base path being wrong.