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
@@ -268,6 +268,9 @@
 	ic->ic_flags_ext |= IEEE80211_FEXT_WATCHDOG;
 #endif
 
+	/* Enable seqno offload */
+	ic->ic_flags_ext |= IEEE80211_FEXT_SEQNO_OFFLOAD;
+
 	/* Adjust capabilities. */
 	rtwn_adj_devcaps(sc);
 
diff --git a/sys/dev/rtwn/if_rtwn_tx.c b/sys/dev/rtwn/if_rtwn_tx.c
--- a/sys/dev/rtwn/if_rtwn_tx.c
+++ b/sys/dev/rtwn/if_rtwn_tx.c
@@ -183,6 +183,10 @@
 		}
 	}
 
+	/* seqno allocate, only if AMPDU isn't running */
+	if ((m->m_flags & M_AMPDU_MPDU) == 0)
+		ieee80211_output_seqno_assign(ni, -1, m);
+
 	cipher = IEEE80211_CIPHER_NONE;
 	if (wh->i_fc[1] & IEEE80211_FC1_PROTECTED) {
 		k = ieee80211_crypto_encap(ni, m);
@@ -229,6 +233,10 @@
 	uint8_t type;
 	u_int cipher;
 
+	/* seqno allocate, only if AMPDU isn't running */
+	if ((m->m_flags & M_AMPDU_MPDU) == 0)
+		ieee80211_output_seqno_assign(ni, -1, m);
+
 	/* Encrypt the frame if need be. */
 	cipher = IEEE80211_CIPHER_NONE;
 	if (params->ibp_flags & IEEE80211_BPF_CRYPTO) {
diff --git a/sys/dev/rtwn/rtl8192c/r92c_tx.c b/sys/dev/rtwn/rtl8192c/r92c_tx.c
--- a/sys/dev/rtwn/rtl8192c/r92c_tx.c
+++ b/sys/dev/rtwn/rtl8192c/r92c_tx.c
@@ -452,6 +452,8 @@
 	} else {
 		uint16_t seqno;
 
+		/* TODO: seqno allocate through net80211? */
+		/* TODO: what to do about QoS NULL frames? */
 		if (m->m_flags & M_AMPDU_MPDU) {
 			seqno = ni->ni_txseqs[tid] % IEEE80211_SEQ_RANGE;
 			ni->ni_txseqs[tid]++;
diff --git a/sys/dev/rtwn/rtl8812a/r12a_tx.c b/sys/dev/rtwn/rtl8812a/r12a_tx.c
--- a/sys/dev/rtwn/rtl8812a/r12a_tx.c
+++ b/sys/dev/rtwn/rtl8812a/r12a_tx.c
@@ -433,6 +433,8 @@
 	} else {
 		uint16_t seqno;
 
+		/* TODO: seqno allocate through net80211? */
+		/* TODO: what to do about QoS NULL frames? */
 		if (m->m_flags & M_AMPDU_MPDU) {
 			seqno = ni->ni_txseqs[tid];
 			ni->ni_txseqs[tid]++;