diff --git a/sys/dev/rtwn/if_rtwn.c b/sys/dev/rtwn/if_rtwn.c
--- a/sys/dev/rtwn/if_rtwn.c
+++ b/sys/dev/rtwn/if_rtwn.c
@@ -271,6 +271,11 @@
 	/* Enable seqno offload */
 	ic->ic_flags_ext |= IEEE80211_FEXT_SEQNO_OFFLOAD;
 
+#ifdef RTWN_WITHOUT_UCODE
+	/* Don't originate NULL data frames - let firmware do this */
+	ic->ic_flags_ext |= IEEE80211_FEXT_NO_NULLDATA;
+#endif
+
 	/* Adjust capabilities. */
 	rtwn_adj_devcaps(sc);