diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index cb31ad917b35..090795c1b65d 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -468,12 +468,10 @@ static struct mbox_chan *
 of_mbox_index_xlate(struct mbox_controller *mbox,
 		    const struct of_phandle_args *sp)
 {
-	int ind = sp->args[0];
-
-	if (ind >= mbox->num_chans)
+	if (sp->args_count < 1 || sp->args[0] >= mbox->num_chans)
 		return ERR_PTR(-EINVAL);
 
-	return &mbox->chans[ind];
+	return &mbox->chans[sp->args[0]];
 }
 
 /**