--- a/ath/if_ath.c
+++ b/ath/if_ath.c
+@@ -10474,11 +10474,11 @@ set_node_txpower(void *arg, struct ieee8
+ * XXX: this function needs some locking to avoid being called
+ * twice/interrupted. Returns the value actually stored. */
+ static u_int32_t
+-ath_set_clamped_maxtxpower(struct ath_softc *sc,
+- u_int32_t new_clamped_maxtxpower)
++ath_set_clamped_maxtxpower(struct ath_softc *sc, u_int32_t new_txpwr)
+ {
+- new_clamped_maxtxpower -= sc->sc_poweroffset;
+- (void)ath_hal_settxpowlimit(sc->sc_ah, new_clamped_maxtxpower);
++ new_txpwr = ((new_txpwr < sc->sc_poweroffset) ? 0 :
++ new_txpwr - sc->sc_poweroffset);
++ (void)ath_hal_settxpowlimit(sc->sc_ah, new_txpwr);
+ return ath_get_clamped_maxtxpower(sc);
+ }
+
@@ -11029,6 +11029,7 @@ enum {
ATH_DEBUG,
ATH_TXANTENNA,