diff --git a/sys/dev/virtio/network/if_vtnet.c b/sys/dev/virtio/network/if_vtnet.c
--- a/sys/dev/virtio/network/if_vtnet.c
+++ b/sys/dev/virtio/network/if_vtnet.c
@@ -1534,6 +1534,15 @@
 		}
 
 		m->m_len = size;
+#ifndef __NO_STRICT_ALIGNMENT
+		/*
+		 * Need to offset the mbuf if the header we're going to add
+		 * will misalign.
+		 */
+		if (sc->vtnet_hdr_size % 4 == 0) {
+			m_adj(m, ETHER_ALIGN);
+		}
+#endif
 		if (m_head != NULL) {
 			m_tail->m_next = m;
 			m_tail = m;
@@ -1560,6 +1569,14 @@
 
 	sc = rxq->vtnrx_sc;
 	clustersz = sc->vtnet_rx_clustersz;
+#ifndef __NO_STRICT_ALIGNMENT
+	/*
+	 * Need to offset the mbuf if the header we're going to add will
+	 * misalign, account for that here.
+	 */
+	if (sc->vtnet_hdr_size % 4 == 0)
+		clustersz -= ETHER_ALIGN;
+#endif
 
 	m_prev = NULL;
 	m_tail = NULL;
@@ -1683,6 +1700,10 @@
 	header_inlined = vtnet_modern(sc) ||
 	    (sc->vtnet_flags & VTNET_FLAG_MRG_RXBUFS) != 0; /* TODO: ANY_LAYOUT */
 
+	/*
+	 * Note: The mbuf has been already adjusted when we allocate it if we
+	 * have to do strict alignment.
+	 */
 	if (header_inlined)
 		error = sglist_append_mbuf(sg, m);
 	else {