ProxyPassReverse not changing the protocol part (https to http) of the redirect url

[Amit Singla <amitsingla82@xxxxxxxxx>]

I need to proxy http requests to https server in the backend. Everything is working except a minor issues in redirects URLs. ProxyPassReverse translates the the URL except the protocol i.e. does not translate https from backend server to http protocol.

Version: Apache/2.2.15

Below is the configuration for reverse proxy

<VirtualHost *:8888>

ServerName frontoffice.example.com

SSLProxyEngine On

ProxyPreserveHost On

ProxyPass /shop https://backend.example.com:9443/shop

ProxyPassReverse /shop  https://backend.example.com:9443/shop

</VirtualHost>

e.g.

http://frontoffice.example.com:8888/shop/cart are proxied to https://backend.example.com:9443/shop/cart.  The backend server results in redirect (302) to https://backend.example.com:9443/shop/login but browser is getting the redirect as 

https://frontoffice.example.com:8888/shop/cart.

So ProxyPassReverse rewrites the URL except the protocol.

Am I missing some configurations here or this is some known issue or expected behavior?

I will appreciate any help on this front.

Thanks