diff --git a/drivers/net/wireless/ath/ath9k/xmit.c b/drivers/net/wireless/ath/ath9k/xmit.c
index 5e2982938ffc3b9e5bc95b803367dfe6141b100e..ac393a6dbe776c29bad426f0ca8e46acbdf4d1dd 100644
--- a/drivers/net/wireless/ath/ath9k/xmit.c
+++ b/drivers/net/wireless/ath/ath9k/xmit.c
@@ -582,7 +582,10 @@ static bool ath_lookup_legacy(struct ath_buf *bf)
 	tx_info = IEEE80211_SKB_CB(skb);
 	rates = tx_info->control.rates;
 
-	for (i = 3; i >= 0; i--) {
+	for (i = 0; i < 4; i++) {
+		if (!rates[i].count || rates[i].idx < 0)
+			break;
+
 		if (!(rates[i].flags & IEEE80211_TX_RC_MCS))
 			return true;
 	}