diff --git a/mt7915/main.c b/mt7915/main.c
index 48b5e205..107baff0 100644
--- a/mt7915/main.c
+++ b/mt7915/main.c
@@ -215,7 +215,7 @@ static int mt7915_add_interface(struct ieee80211_hw *hw,
 	mvif->phy = phy;
 	mvif->band_idx = ext_phy;
 
-	if (ext_phy)
+	if (dev->mt76.phy2)
 		mvif->wmm_idx = ext_phy * (MT7915_MAX_WMM_SETS / 2) +
 				mvif->idx % (MT7915_MAX_WMM_SETS / 2);
 	else