Asterisk and SRTP

I am using Asterisk (original) v1.8.9.2 compiled with Lib SRTP 1.4.2.

In the phone and provider trunks I have:
encryption = yes

When making an outgoing call I am getting the message:

[Feb 16 17:50:43] WARNING[4636]: sip/sdp_crypto.c:167 sdp_crypto_activate: Could not set local SRTP policy

I am using a Yealink T28P phone (SRTP turned on) and a upline provider who support SRTP (They are using Asterisk as well).

When calling another extension (Also a T28P with SRTP support turned on) on the same PBX I do not get this message.