diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index a49b6ce750..0ab1251737 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -2903,6 +2903,8 @@ static void *_sip_tcp_helper_thread(struct sip_pvt *pvt, struct ast_tcptls_sessi
 		reqcpy.data = str_save;
 		ast_str_reset(reqcpy.data);
 
+		memset(buf, 0, sizeof(buf));
+
 		if (tcptls_session->ssl) {
 			set_socket_transport(&req.socket, SIP_TRANSPORT_TLS);
 			req.socket.port = htons(ourport_tls);