Here is the patch for 2.7.

Changes are in Sources/AOChat.php

Change
AOCP_LOGIN_CHARID       => array("name"=>"Login CharacterID",                   "args"=>"III"),
to
AOCP_LOGIN_CHARID       => array("name"=>"Login CharacterID",                   "args"=>"IIIS"),

Change ( line 468 ish AND 935 ish )
 $loginCharacterPacket = new AOChatPacket("out", AOCP_LOGIN_CHARID, array(1,$this->char["id"],$this->serverseed ) );
to
 $loginCharacterPacket = new AOChatPacket("out", AOCP_LOGIN_CHARID, array(1,$this->char["id"],$this->serverseed, "en") );

I also attached the whole file if you just want to replace it with the changes.