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
@@ -5681,8 +5681,9 @@
 	if (rinfo == NULL)
 		return EINVAL;
 
-	/* Offloaded sequence number assignment */
-	/* Note: Should be done in firmware on all supported devices */
+	/* Offloaded sequence number assignment; non-AMPDU case */
+	if ((m->m_flags & M_AMPDU_MPDU) == 0)
+		ieee80211_output_seqno_assign(ni, -1, m);
 
 	/* Radiotap */
 	if (ieee80211_radiotap_active_vap(vap)) {