--- a/sys/netproto/802_11/wlan/ieee80211.c
+++ b/sys/netproto/802_11/wlan/ieee80211.c
@@ -1620 ieee80211_media_setup / maxrate()
 		i = ic->ic_txstream * 8 - 1;
+		if (i >= IEEE80211_HTRATE_MAXSIZE)	/* DF-3343: clamp */
+			i = IEEE80211_HTRATE_MAXSIZE - 1;
 		if ((ic->ic_htcaps & IEEE80211_HTCAP_CHWIDTH40) &&