diff --git a/libpri.h b/libpri.h
index 9d89b53..6ffb45e 100755
--- a/libpri.h
+++ b/libpri.h
@@ -48,6 +48,7 @@
 #define PRI_SWITCH_ATT4ESS		4	/* AT&T 4ESS */
 #define PRI_SWITCH_EUROISDN_E1	5	/* Standard EuroISDN (CTR4, ETSI 300-102) */
 #define PRI_SWITCH_EUROISDN_T1	6	/* T1 EuroISDN variant (ETSI 300-102) */
+#define PRI_SWITCH_NI1			7	/* National ISDN 1 */
 
 /* PRI D-Channel Events */
 #define PRI_EVENT_DCHAN_UP	 	1	/* D-channel is up */
diff --git a/pri.c b/pri.c
index ee9444a..b55e520 100755
--- a/pri.c
+++ b/pri.c
@@ -49,6 +49,8 @@ char *pri_switch2str(int sw)
 		return "Lucent 5E";
 	case PRI_SWITCH_ATT4ESS:
 		return "AT&T 4ESS";
+	case PRI_SWITCH_NI1:
+		return "National ISDN 1";
 	default:
 		return "Unknown switchtype";
 	}
diff --git a/q931.c b/q931.c
index 6bc4796..00a71c8 100755
--- a/q931.c
+++ b/q931.c
@@ -911,9 +911,12 @@ static int receive_display(struct pri *pri, q931_call *call, int msgtype, q931_i
 
 static int transmit_display(struct pri *pri, q931_call *call, int msgtype, q931_ie *ie, int len)
 {
-	ie->data[0] = 0xb1;
-	memcpy(ie->data + 1, call->callername, strlen(call->callername));
-	return 3 + strlen(call->callername);
+	if (pri->switchtype != PRI_SWITCH_NI1) {
+		ie->data[0] = 0xb1;
+		memcpy(ie->data + 1, call->callername, strlen(call->callername));
+		return 3 + strlen(call->callername);
+	}
+	return 0;
 }
 
 static int receive_progress_indicator(struct pri *pri, q931_call *call, int msgtype, q931_ie *ie, int len)