Captive portal and pptp firewall rules?

[question]

I'm using version 1.2.3-RC3 
I have a captive portal set up for my clients. At the moment it only allows http traffic through.
I want to allow pptp vpn connections through as well. I've tried changing the firewall rules to allow pptp traffic to pass through but it still doesn't work.

I've check the wireless router and it allows for pptp traffic to pass through so I know it's not blocking it.

Anyone know how I can set it up to allow pptp traffic to pass through?

Thanks