I am trying to use the following configuration: <LocationMatch "(.*\.(html|htm))$"> ErrorDocument 404 "/error-404.html" </LocationMatch> <Location "/error-404.html"> RequestHeader set customheader "%{ENV:REDIRECT_URL}e" ProxyPass "http://otherhost.org/" ProxyPassReverse "http://otherhost.org/" </Location> So ErrorDocument internally redirects to error-404.html, and in so doing sets a header REDIRECT_URL = original URL. I then want to proxy the reques to otherhost.org, setting the original URL as a request header. Everything works, except for that REDIRECT_URL apparently is not yet available when the <Location> directives are executed, because 'customheader' above always gets set to just '{null}'. So my feature enhancement suggestion is that REDIRECT_URL be made available somehow in the <Location>.