diff --git a/mac80211.c b/mac80211.c
index a962abce..686d9b97 100644
--- a/mac80211.c
+++ b/mac80211.c
@@ -641,7 +641,7 @@ mt76_airtime_flush_ampdu(struct mt76_dev *dev)
 		return;
 
 	wcid_idx = dev->rx_ampdu_status.wcid_idx;
-	if (dev->rx_ampdu_status.wcid_idx != 0xff)
+	if (wcid_idx < ARRAY_SIZE(dev->wcid))
 		wcid = rcu_dereference(dev->wcid[wcid_idx]);
 	else
 		wcid = NULL;