Apache query string rewrite not working

I need to rewrite a domain name in a query parameter in order to augment a proxy. The proxy basically is just a domain rewrite, but some of the responses from the upstream server include a query parameter that is eventually used as a redirect (in the "Location" header). I need to be able to rewrite this domain name so that it points to the proxy instead of the upstream server. My current config looks like SSLEngine On SSLProxyEngine On # Set the path to SSL certificate # Usage: SSLCertificateFile /path/to/cert.pem SSLCertificateFile /etc/apache2/ssl/apache.crt SSLCertificateKeyFile /etc/apache2/ssl/apache.key # Servers to proxy the connection, or; # List of application servers: # Usage: # ProxyPass / http://[IP Addr.]:[port]/ # ProxyPassReverse / http://[IP Addr.]:[port]/ # Example: RewriteEngine On LogLevel alert rewrite:trace6 RewriteCond %{QUERY_STRING} (.*)upstream\.com(.*) RewriteRule (.*)upstream\.com(.*) %1proxy.com%2 [N] ProxyPass / https://upstream.com/ ProxyPassReverse / https://upstream.com/ The proxy is working fine, but one of the first things the upstream server does is send a redirect with a query parameter that is used for a second redirect, which causes the proxy to lose control of the traffic stream. I need this query string rewritten so the upstream servers response will cause a redirect back to the proxy instead of the upstream server. mod_rewrite is enabled and 'apachectl -t' reports that the config is OK.