diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 1aaa73fa308e655e013970e2abeb0d5da7cb4bb5..b5c06242a92e5b9667760b3bfada218256e63cc8 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -1967,6 +1967,16 @@ ieee80211_sta_wmm_params(struct ieee80211_local *local,
 		ieee80211_regulatory_limit_wmm_params(sdata, &params[ac], ac);
 	}
 
+	/* WMM specification requires all 4 ACIs. */
+	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
+		if (params[ac].cw_min == 0) {
+			sdata_info(sdata,
+				   "AP has invalid WMM params (missing AC %d), using defaults\n",
+				   ac);
+			return false;
+		}
+	}
+
 	for (ac = 0; ac < IEEE80211_NUM_ACS; ac++) {
 		mlme_dbg(sdata,
 			 "WMM AC=%d acm=%d aifs=%d cWmin=%d cWmax=%d txop=%d uapsd=%d, downgraded=%d\n",