diff --git a/drivers/staging/speakup/spk_ttyio.c b/drivers/staging/speakup/spk_ttyio.c
index 93742dbdee77bbde7290ef039f1076b5b856dcfd..6c754ddf125710736cf4456149a5f81ec1a1a1f4 100644
--- a/drivers/staging/speakup/spk_ttyio.c
+++ b/drivers/staging/speakup/spk_ttyio.c
@@ -49,15 +49,25 @@ static int spk_ttyio_ldisc_open(struct tty_struct *tty)
 
 	if (tty->ops->write == NULL)
 		return -EOPNOTSUPP;
+
+	mutex_lock(&speakup_tty_mutex);
+	if (speakup_tty) {
+		mutex_unlock(&speakup_tty_mutex);
+		return -EBUSY;
+	}
 	speakup_tty = tty;
 
 	ldisc_data = kmalloc(sizeof(struct spk_ldisc_data), GFP_KERNEL);
-	if (!ldisc_data)
+	if (!ldisc_data) {
+		speakup_tty = NULL;
+		mutex_unlock(&speakup_tty_mutex);
 		return -ENOMEM;
+	}
 
 	sema_init(&ldisc_data->sem, 0);
 	ldisc_data->buf_free = true;
 	speakup_tty->disc_data = ldisc_data;
+	mutex_unlock(&speakup_tty_mutex);
 
 	return 0;
 }