Blindtransfer variable after pickup


i have a situation where i have a receptionist that is not always there.
All incomming calls ring this extension, when she is not there the other users pickup the extension with *8 to answer the call.
When they then try to do a blind transfer with the phones blindtransfer feature asterisk does not give anything in the variable ${blindtransfer}.
if they answer a call when the phone rings and not use *8 it does give the blindtransfer variable
is this a pickup bug in asterisk? where the tT options are not passed to the extension that answerd the call?
and is there a way to workarround this bug