Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(revision 351503)
+++ channels/chan_sip.c	(working copy)
@@ -30139,6 +30139,12 @@
 
 static int process_crypto(struct sip_pvt *p, struct ast_rtp_instance *rtp, struct sip_srtp **srtp, const char *a)
 {
+	/* If no RTP instance exists for this media stream don't bother processing the crypto line */
+	if (!rtp) {
+		ast_debug(3, "Received offer with crypto line for media stream that is not enabled\n");
+		return FALSE;
+	}
+
 	if (strncasecmp(a, "crypto:", 7)) {
 		return FALSE;
 	}