IAuthenticationRequest.RedirectToProvider Is Not Supposed To Return

The method DotNetOpenAuth.OpenId.RelyingParty.IAuthenticationRequest.RedirectToProvider() is documented never to return:

Redirects the user agent to the provider for authentication. Execution of the current page terminates after this call.

However, it does return under the latest implementation (3.4.3). I'm using the following code:

using (var relayingParty = new OpenIdRelyingParty())
{
var response = relayingParty.GetResponse();
if (response == null)
{
// Stage 2: user submitting Identifier
var openId = Request.Form["openId"];
relayingParty.CreateRequest(openId).RedirectToProvider();
throw new Exception("Never gets here");
}
...
}

(The line with "Never gets here" is reached). I need to return an ActionResult from this method ...