I inherited a codebase and I am trying to upgrade it locally (at this stage, 4.7.2 to 4.8.1) and, when navigating to /install/default.aspx as I normally do when upgrading, application is redirecting me to /install/default (without the *.aspx extension). I do see these entries in my web.config:

<add key="umbracoReservedUrls" value="~/config/splashes/booting.aspx,~/install/default.aspx,~/config/splashes/noNodes.aspx" />
<add key="umbracoReservedPaths" value="~/umbraco,~/install/" /

...which I thought were supposed to override the URL rewriting in particular paths, but it appears not to be working. What is wrong with this picture? Obviously /install//default is a blank page so I can't get the wizard to run.

Any help much appreciated in advance!

Thanks, Garrett