+--- a/ath/if_ath.c
++++ b/ath/if_ath.c
+@@ -4914,7 +4914,7 @@
+ * capability info and arrange for a mode change
+ * if needed.
+ */
+- if (sc->sc_dturbo) {
++ if (sc->sc_dturbo && NULL != avp->av_boff.bo_tim) {
+ u_int8_t dtim;
+ dtim = ((avp->av_boff.bo_tim[2] == 1) ||
+ (avp->av_boff.bo_tim[3] == 1));