diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index eba51460a5ded4b6456a18b946153c6a310bdb48..f39f504cc3a0870bd57605c0f944d59bb82f9524 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -685,11 +685,16 @@ static void mac80211_hwsim_set_tsf(struct ieee80211_hw *hw,
 	struct mac80211_hwsim_data *data = hw->priv;
 	u64 now = mac80211_hwsim_get_tsf(hw, vif);
 	u32 bcn_int = data->beacon_int;
-	s64 delta = tsf - now;
+	u64 delta = abs64(tsf - now);
 
-	data->tsf_offset += delta;
 	/* adjust after beaconing with new timestamp at old TBTT */
-	data->bcn_delta = do_div(delta, bcn_int);
+	if (tsf > now) {
+		data->tsf_offset += delta;
+		data->bcn_delta = do_div(delta, bcn_int);
+	} else {
+		data->tsf_offset -= delta;
+		data->bcn_delta = -do_div(delta, bcn_int);
+	}
 }
 
 static void mac80211_hwsim_monitor_rx(struct ieee80211_hw *hw,