--- a/ath/if_ath.c
+++ b/ath/if_ath.c
@@ -4917,7 +4917,7 @@
 	 * 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));