diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index 23b014b8c91993706bbde23505a172f85e2b5a77..94c963462d74b1ff5356e2ce39b9b08482d95839 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -2159,12 +2159,13 @@ static void gsm_error(struct gsm_mux *gsm,
 static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 {
 	int i;
-	struct gsm_dlci *dlci = gsm->dlci[0];
+	struct gsm_dlci *dlci;
 	struct gsm_msg *txq, *ntxq;
 
 	gsm->dead = true;
 	mutex_lock(&gsm->mutex);
 
+	dlci = gsm->dlci[0];
 	if (dlci) {
 		if (disc && dlci->state != DLCI_CLOSED) {
 			gsm_dlci_begin_close(dlci);
@@ -2178,8 +2179,10 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 
 	/* Free up any link layer users and finally the control channel */
 	for (i = NUM_DLCI - 1; i >= 0; i--)
-		if (gsm->dlci[i])
+		if (gsm->dlci[i]) {
 			gsm_dlci_release(gsm->dlci[i]);
+			gsm->dlci[i] = NULL;
+		}
 	mutex_unlock(&gsm->mutex);
 	/* Now wipe the queues */
 	tty_ldisc_flush(gsm->tty);