Steps to reproduce:

1. Visit https://doc.rust-lang.org/nughtly/std.
2. Get a 404 page with a search box.
3. Type "string" in the search and hit enter.

Expected result: go to https://doc.rust-lang.org/std/index.html?search=string (successful response)

Actual result: go to https://doc.rust-lang.org/nughtly/std/index.html?search=string (still a 404)

Note: everything works fine with a path that has no slash, e.g. https://doc.rust-lang.org/nughtly