diff --git a/sys/dev/iwx/if_iwx.c b/sys/dev/iwx/if_iwx.c
--- a/sys/dev/iwx/if_iwx.c
+++ b/sys/dev/iwx/if_iwx.c
@@ -5683,6 +5683,9 @@
 
 	/* Offloaded sequence number assignment */
 	/* Note: Should be done in firmware on all supported devices */
+	/* seqno allocate, only if AMPDU isn't running */
+	if ((m->m_flags & M_AMPDU_MPDU) == 0)
+		ieee80211_output_seqno_assign(ni, -1, m);
 
 	/* Radiotap */
 	if (ieee80211_radiotap_active_vap(vap)) {