--- chan_sip.c.buggy	2013-02-18 14:42:57.000000000 +0100
+++ chan_sip.c	2013-02-18 14:44:44.000000000 +0100
@@ -11881,7 +11881,7 @@
 		/* Prefer the audio codec we were requested to use, first, no matter what
 		   Note that p->prefcodec can include video codecs, so mask them out
 		*/
-		if (capability & p->prefcodec) {
+		if ((capability & p->prefcodec) & AST_FORMAT_AUDIO_MASK) {
 			format_t codec = p->prefcodec & AST_FORMAT_AUDIO_MASK;
 
 			add_codec_to_sdp(p, codec, &m_audio, &a_audio, debug, &min_audio_packet_size);