diff -urN asterisk-11.2.1.orig/channels/chan_sip.c asterisk-11.2.1/channels/chan_sip.c
--- asterisk-11.2.1.orig/channels/chan_sip.c	2013-01-09 12:43:00.000000000 -0800
+++ asterisk-11.2.1/channels/chan_sip.c	2013-03-25 12:47:33.491194437 -0700
@@ -7417,6 +7417,10 @@
 	struct sip_pvt *p = ast_channel_tech_pvt(ast);
 	int res = 0;
 
+	if (!p) {
+		return -1;
+	}
+
 	sip_pvt_lock(p);
 	switch (ast_test_flag(&p->flags[0], SIP_DTMF)) {
 	case SIP_DTMF_INBAND:
@@ -7441,6 +7445,10 @@
 	struct sip_pvt *p = ast_channel_tech_pvt(ast);
 	int res = 0;
 
+	if (!p) {
+		return -1;
+	}
+
 	sip_pvt_lock(p);
 	switch (ast_test_flag(&p->flags[0], SIP_DTMF)) {
 	case SIP_DTMF_INFO:
diff -urN asterisk-11.2.1.orig/main/channel.c asterisk-11.2.1/main/channel.c
--- asterisk-11.2.1.orig/main/channel.c	2013-01-09 12:43:00.000000000 -0800
+++ asterisk-11.2.1/main/channel.c	2013-03-25 13:02:38.522195090 -0700
@@ -4738,8 +4738,9 @@
 		"941+1209", /* * */
 		"941+1477"  /* # */
 	};
+	struct ast_channel_tech *tech = ast_channel_tech(chan);
 
-	if (!ast_channel_tech(chan)->send_digit_begin)
+	if (!tech->send_digit_begin)
 		return 0;
 
 	ast_channel_lock(chan);
@@ -4747,7 +4748,7 @@
 	ast_channel_sending_dtmf_tv_set(chan, ast_tvnow());
 	ast_channel_unlock(chan);
 
-	if (!ast_channel_tech(chan)->send_digit_begin(chan, digit))
+	if (!tech->send_digit_begin(chan, digit))
 		return 0;
 
 	if (digit >= '0' && digit <='9')
@@ -4769,9 +4770,10 @@
 int ast_senddigit_end(struct ast_channel *chan, char digit, unsigned int duration)
 {
 	int res = -1;
+	struct ast_channel_tech *tech = ast_channel_tech(chan);
 
-	if (ast_channel_tech(chan)->send_digit_end)
-		res = ast_channel_tech(chan)->send_digit_end(chan, digit, duration);
+	if (tech->send_digit_end)
+		res = tech->send_digit_end(chan, digit, duration);
 
 	ast_channel_lock(chan);
 	if (ast_channel_sending_dtmf_digit(chan) == digit) {