Alcatel OmniAccess AP1101 and External Captive Portal

[one0fnine]

Hi all!
I'm trying to setup external captive portal on this AP. To use HTTPS redirect option I've bought SSL certificate and uploaded it like External Captive Portal Certificate. JIC I disabled Client Behavior Tracking options too. But when i'm connecting to my captive portal I get certificate error. That the certificate is untrusted. The AP intercepts requests to the portal and adds its untrusted certificate, like MITM SSL proxy.
So ... how can i change root ca certificate? or how can disable this option of intercepting SSL certificates.