pfSense RADIUS challenge

I'm trying to configure my pfSense box (running 2.5.2-RELEASE) to use my RADIUS server for admin login authentication.

My RADIUS server challenges for a TOTP code after getting the correct password, and this is working correctly (I have a number of other systems here using it for login).

I've configured my pfSense box with a RADIUS server (User Manager->Authentication Server) and I've set pfSense to try to authenticate via the RADIUS server (User Manager->Settings, select the RADIUS server).

If I watch the activity on the RADIUS server, I can see pfSense asking for authentication, and then the RADIUS server replying with a challenge for the TOTP code. pfSense doesn't appear to be able to deal with the challenge.

Is there anyway to get pfSense to do the right thing here? Or do I have to add support for entering the TOTP code with the password to my RADIUS server?