Unable to use g729a codec from Digium

I have successfully registered and installed the digium g729a codec on freepbx 13 ( with asterisk 13), but when trying to make a call I get the following error in the asterisk log

[2017-04-13 16:42:16] WARNING[28657][C-00000039]: channel.c:5610 set_format: Unable to find a codec translation path: (g729) -> (alaw)
[2017-04-13 16:42:16] WARNING[28657][C-00000039]: translate.c:492 ast_translator_build_path: No translator path from g729 to slin
[2017-04-13 16:42:16] WARNING[28657][C-00000039]: chan_sip.c:7734 sip_write: Asked to transmit frame type g729, while native formats is (alaw) read/write = g729/g729

I’ve spoken to digium, they said it had registered ok, but they were unable to help as it was installed on a freepbx system, and to speak to the freepbx community instead.

Can anyone help get this fixed?