Reverse Proxy using Admininstration for SSL weird URL error

I am using a proxy server (www.my-example.com) to a localhost:9080 backend server.

My proxy configuration excerpt for both *.80 and *.443 files:

ProxyPreserveHost On
ProxyRequests Off
ProxyPass / http://localhost:9080/firstsite/
ProxyPassReverse / http://localhost:9080/firstsite/

I followed the WP Codex instructions on Administration over SSL. If I put FORCE_SSL_ADMIN to false, I can proxy to my backend server without any problems including Login and Administration pages. However, with FORCE_SSL_ADMIN is true, those non-SSL pages are fine but Login and Administration pages will throw an URL of:
https://www.my-example.com/firstsite/firstsite/wp-login.php
Notice the double “/firstsite/firstsite” in the URL. I even try removing the Administration over SSL and use the VerveSSL plugin, and it does the same thing when I turn on SSL. Also, with the following, it still doesn’t work:
ProxyPassReverse / http://localhost:9080/firstsite/firstsite/