diff --git a/net/mac80211/rate.c b/net/mac80211/rate.c
index a02bef35b134..d68d6cfac3b5 100644
--- a/net/mac80211/rate.c
+++ b/net/mac80211/rate.c
@@ -448,7 +448,7 @@ static void rate_fixup_ratelist(struct ieee80211_vif *vif,
 	 */
 	if (!(rates[0].flags & IEEE80211_TX_RC_MCS)) {
 		u32 basic_rates = vif->bss_conf.basic_rates;
-		s8 baserate = basic_rates ? ffs(basic_rates - 1) : 0;
+		s8 baserate = basic_rates ? ffs(basic_rates) - 1 : 0;
 
 		rate = &sband->bitrates[rates[0].idx];