diff --git a/sys/dev/hyperv/vmbus/vmbus_chan.c b/sys/dev/hyperv/vmbus/vmbus_chan.c
--- a/sys/dev/hyperv/vmbus/vmbus_chan.c
+++ b/sys/dev/hyperv/vmbus/vmbus_chan.c
@@ -1555,7 +1555,7 @@
 			continue;
 
 		flags = atomic_swap_long(&event_flags[f], 0);
-		chid_base = f << VMBUS_EVTFLAG_SHIFT;
+		chid_base = f * VMBUS_EVTFLAG_LEN;
 
 		while ((chid_ofs = ffsl(flags)) != 0) {
 			struct vmbus_channel *chan;
@@ -1599,7 +1599,7 @@
 	eventf = VMBUS_PCPU_GET(sc, event_flags, cpu) + VMBUS_SINT_MESSAGE;
 	if (atomic_testandclear_long(&eventf->evt_flags[0], 0)) {
 		vmbus_event_flags_proc(sc, sc->vmbus_rx_evtflags,
-		    VMBUS_CHAN_MAX_COMPAT >> VMBUS_EVTFLAG_SHIFT);
+		    VMBUS_CHAN_MAX_COMPAT / VMBUS_EVTFLAG_LEN);
 	}
 }
 
@@ -1903,7 +1903,7 @@
 	 * Setup event flag.
 	 */
 	chan->ch_evtflag =
-	    &sc->vmbus_tx_evtflags[chan->ch_id >> VMBUS_EVTFLAG_SHIFT];
+	    &sc->vmbus_tx_evtflags[chan->ch_id / VMBUS_EVTFLAG_LEN];
 	chan->ch_evtflag_mask = 1UL << (chan->ch_id & VMBUS_EVTFLAG_MASK);
 
 	/*
diff --git a/sys/dev/hyperv/vmbus/vmbus_reg.h b/sys/dev/hyperv/vmbus/vmbus_reg.h
--- a/sys/dev/hyperv/vmbus/vmbus_reg.h
+++ b/sys/dev/hyperv/vmbus/vmbus_reg.h
@@ -60,16 +60,10 @@
  * Hyper-V SynIC event flags
  */
 
-#ifdef __LP64__
-#define VMBUS_EVTFLAGS_MAX	32
-#define VMBUS_EVTFLAG_SHIFT	6
-#else
-#define VMBUS_EVTFLAGS_MAX	64
-#define VMBUS_EVTFLAG_SHIFT	5
-#endif
-#define VMBUS_EVTFLAG_LEN	(1 << VMBUS_EVTFLAG_SHIFT)
+#define VMBUS_EVTFLAG_LEN	(sizeof(u_long) * 8)
 #define VMBUS_EVTFLAG_MASK	(VMBUS_EVTFLAG_LEN - 1)
 #define VMBUS_EVTFLAGS_SIZE	256
+#define VMBUS_EVTFLAGS_MAX	(VMBUS_EVTFLAGS_SIZE / sizeof(u_long))
 
 struct vmbus_evtflags {
 	u_long		evt_flags[VMBUS_EVTFLAGS_MAX];