diff --git a/sys/net80211/ieee80211_freebsd.h b/sys/net80211/ieee80211_freebsd.h
--- a/sys/net80211/ieee80211_freebsd.h
+++ b/sys/net80211/ieee80211_freebsd.h
@@ -341,11 +341,16 @@
 #define	M_AGE_SUB(m,adj)	(m->m_pkthdr.csum_data -= adj)
 
 /*
- * Store the sequence number.
+ * Store / retrieve the sequence number in an mbuf.
+ *
+ * The sequence number being stored/retreived is the 12 bit
+ * base sequence number, not the 16 bit sequence number field.
+ * I.e., it's from 0..4095 inclusive, with no 4 bit padding for
+ * fragment numbers.
  */
 #define	M_SEQNO_SET(m, seqno) \
-	((m)->m_pkthdr.tso_segsz = (seqno))
-#define	M_SEQNO_GET(m)	((m)->m_pkthdr.tso_segsz)
+	((m)->m_pkthdr.tso_segsz = ((seqno) % IEEE80211_SEQ_RANGE))
+#define	M_SEQNO_GET(m)	(((m)->m_pkthdr.tso_segsz) % IEEE80211_SEQ_RANGE)
 
 #define	MTAG_ABI_NET80211	1132948340	/* net80211 ABI */