asterisk users - Jul 2014 - Return to transferor if no answer after REFER

Hi all,

Consider the following scenario. Extension A is in a call with B. At
some point, B transfers A to C by sending REFER:

   A              Asterisk               B                 C
   |                  |                  |                 |
   |<-- INVITE/200 -->|<-- INVITE/200 -->|                 |
   :                  :                  :                 :
   |                  |<--- REFER A r: C |                 |
   |                  | 200 OK --------->|                 |
   |                  | INVITE C ------------------------->|
   |                  | NOTIFY --------->|                 |
   :                  :                  :                 :

If the INVITE to C is answered, B is connected to C, and A is hung up
(receives BYE), which is the expected behaviour.

However, if C does not answer (is busy, etc), Asterisk hangs up on A and
B anyway. What I'd like to have is to connect B back to A instead.

Is this possible, and if yes, what am I missing? Any pointers are
welcome.

Thanks,
J?nis