diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c
index 537f4f6d009b..674b35f402f5 100644
--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -351,7 +351,7 @@ struct mbox_chan *mbox_request_channel(struct mbox_client *cl, int index)
 	init_completion(&chan->tx_complete);
 
 	if (chan->txdone_method	== TXDONE_BY_POLL && cl->knows_txdone)
-		chan->txdone_method |= TXDONE_BY_ACK;
+		chan->txdone_method = TXDONE_BY_ACK;
 
 	spin_unlock_irqrestore(&chan->lock, flags);
 
@@ -418,7 +418,7 @@ void mbox_free_channel(struct mbox_chan *chan)
 	spin_lock_irqsave(&chan->lock, flags);
 	chan->cl = NULL;
 	chan->active_req = NULL;
-	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
+	if (chan->txdone_method == TXDONE_BY_ACK)
 		chan->txdone_method = TXDONE_BY_POLL;
 
 	module_put(chan->mbox->dev->driver->owner);
diff --git a/drivers/mailbox/pcc.c b/drivers/mailbox/pcc.c
index 9b7005e1345e..27c2294be51a 100644
--- a/drivers/mailbox/pcc.c
+++ b/drivers/mailbox/pcc.c
@@ -266,7 +266,7 @@ struct mbox_chan *pcc_mbox_request_channel(struct mbox_client *cl,
 	init_completion(&chan->tx_complete);
 
 	if (chan->txdone_method == TXDONE_BY_POLL && cl->knows_txdone)
-		chan->txdone_method |= TXDONE_BY_ACK;
+		chan->txdone_method = TXDONE_BY_ACK;
 
 	spin_unlock_irqrestore(&chan->lock, flags);
 
@@ -312,7 +312,7 @@ void pcc_mbox_free_channel(struct mbox_chan *chan)
 	spin_lock_irqsave(&chan->lock, flags);
 	chan->cl = NULL;
 	chan->active_req = NULL;
-	if (chan->txdone_method == (TXDONE_BY_POLL | TXDONE_BY_ACK))
+	if (chan->txdone_method == TXDONE_BY_ACK)
 		chan->txdone_method = TXDONE_BY_POLL;
 
 	spin_unlock_irqrestore(&chan->lock, flags);