Invalid radius attribute

I have been using MT 2.9 and icradius as radius server and shaping the traffic to my user using radius attribute as Ascend-Data-Rate.This is working perfectly but the problem with it I can’t burst the bandwidth value. So I tried to attribute Mikrotik-Rate-Limit but when assigned it to my user, in radius log shows Error: unknown attribute Mikrotik-Rate-Limit.
Can anyone help me to use this attribute(Mikrotik-Rate-Limit) in icradius.

Thanks
Rocky

We use Ascend-Data-Rate

SMA