diff --git a/channels/chan_zap.c b/channels/chan_zap.c
index 8c5f25d23..cc17af93b 100644
--- a/channels/chan_zap.c
+++ b/channels/chan_zap.c
@@ -1150,9 +1150,9 @@ static int zt_digit_begin(struct ast_channel *chan, char digit)
 			.op = ZT_DIAL_OP_APPEND,
 		};
 
-		dialstr[0] = 'T';
-		dialstr[1] = digit;
-		dialstr[2] = '\0';
+		zo.dialstr[0] = 'T';
+		zo.dialstr[1] = digit;
+		zo.dialstr[2] = '\0';
 		if ((res = ioctl(pvt->subs[SUB_REAL].zfd, ZT_DIAL, &zo)))
 			ast_log(LOG_WARNING, "Couldn't dial digit %c\n", digit);
 		else