Index: head/sys/dev/hyperv/include/hyperv.h
===================================================================
--- head/sys/dev/hyperv/include/hyperv.h
+++ head/sys/dev/hyperv/include/hyperv.h
@@ -629,6 +629,7 @@
 
 	struct task			ch_detach_task;
 	TAILQ_ENTRY(hv_vmbus_channel)	ch_link;
+	uint32_t			ch_subidx;	/* subchan index */
 
 	struct sysctl_ctx_list		ch_sysctl_ctx;
 } hv_vmbus_channel;
Index: head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
===================================================================
--- head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
+++ head/sys/dev/hyperv/netvsc/hv_netvsc_drv_freebsd.c
@@ -518,9 +518,9 @@
 	 */
 	pri_chan = device_ctx->channel;
 	KASSERT(HV_VMBUS_CHAN_ISPRIMARY(pri_chan), ("not primary channel"));
-	KASSERT(pri_chan->offer_msg.offer.sub_channel_index == 0,
+	KASSERT(pri_chan->ch_subidx == 0,
 	    ("primary channel subidx %u",
-	     pri_chan->offer_msg.offer.sub_channel_index));
+	     pri_chan->ch_subidx));
 	hn_channel_attach(sc, pri_chan);
 
 	ifp->if_flags = IFF_BROADCAST | IFF_SIMPLEX | IFF_MULTICAST;
@@ -809,8 +809,8 @@
 	txr = txd->txr;
 	KASSERT(txr->hn_chan == chan,
 	    ("channel mismatch, on channel%u, should be channel%u",
-	     chan->offer_msg.offer.sub_channel_index,
-	     txr->hn_chan->offer_msg.offer.sub_channel_index));
+	     chan->ch_subidx,
+	     txr->hn_chan->ch_subidx));
 
 	txr->hn_has_txeof = 1;
 	hn_txdesc_put(txr, txd);
@@ -2940,7 +2940,7 @@
 	struct hn_rx_ring *rxr;
 	int idx;
 
-	idx = chan->offer_msg.offer.sub_channel_index;
+	idx = chan->ch_subidx;
 
 	KASSERT(idx >= 0 && idx < sc->hn_rx_ring_inuse,
 	    ("invalid channel index %d, should > 0 && < %d",
@@ -2981,9 +2981,9 @@
 
 	KASSERT(!HV_VMBUS_CHAN_ISPRIMARY(chan),
 	    ("subchannel callback on primary channel"));
-	KASSERT(chan->offer_msg.offer.sub_channel_index > 0,
+	KASSERT(chan->ch_subidx > 0,
 	    ("invalid channel subidx %u",
-	     chan->offer_msg.offer.sub_channel_index));
+	     chan->ch_subidx));
 	hn_channel_attach(sc, chan);
 }
 
Index: head/sys/dev/hyperv/vmbus/hv_channel.c
===================================================================
--- head/sys/dev/hyperv/vmbus/hv_channel.c
+++ head/sys/dev/hyperv/vmbus/hv_channel.c
@@ -111,7 +111,7 @@
 	} else {
 		dev = primary_ch->device->device;
 		ch_id = primary_ch->ch_id;
-		sub_ch_id = channel->offer_msg.offer.sub_channel_index;
+		sub_ch_id = channel->ch_subidx;
 	}
 	ctx = &channel->ch_sysctl_ctx;
 	sysctl_ctx_init(ctx);
Index: head/sys/dev/hyperv/vmbus/hv_channel_mgmt.c
===================================================================
--- head/sys/dev/hyperv/vmbus/hv_channel_mgmt.c
+++ head/sys/dev/hyperv/vmbus/hv_channel_mgmt.c
@@ -152,14 +152,14 @@
 		}
 		device_printf(sc->vmbus_dev, "chan%u subchanid%u offer%s\n",
 		    new_channel->ch_id,
-		    new_channel->offer_msg.offer.sub_channel_index, logstr);
+		    new_channel->ch_subidx, logstr);
 	}
 
 	if (channel != NULL) {
 		/*
 		 * Check if this is a sub channel.
 		 */
-		if (new_channel->offer_msg.offer.sub_channel_index != 0) {
+		if (new_channel->ch_subidx != 0) {
 			/*
 			 * It is a sub channel offer, process it.
 			 */
@@ -293,6 +293,7 @@
 	/* Allocate the channel object and save this offer */
 	new_channel = hv_vmbus_allocate_channel(sc);
 	new_channel->ch_id = offer->child_rel_id;
+	new_channel->ch_subidx = offer->offer.sub_channel_index;
 
 	/*
 	 * By default we setup state to enable batched