I'm trying to setup a custom error page for the IIS 7 404.13 (Content length too large) error. Here's the relevant sections of my web.config file:

<system.webServer>
  <httpErrors errorMode="Custom" existingResponse="Replace">
    <remove statusCode="404" subStatusCode="13" />
    <error statusCode="404" subStatusCode="13" prefixLanguageFilePath="" path="/FileUpload/Test.aspx" responseMode="ExecuteURL" />
  </httpErrors>
  <security>
    <requestFiltering>
      <requestLimits maxAllowedContentLength="10240" />
    </requestFiltering>
  </security>
</system.webServer>

The response that is being sent back to the server is blank. The Test.aspx file is not blank.

Any idea what's going on here?