diff --git a/hypervisor/common/event.c b/hypervisor/common/event.c
index e05cd963c..b58dc27f2 100644
--- a/hypervisor/common/event.c
+++ b/hypervisor/common/event.c
@@ -11,7 +11,7 @@
 void init_event(struct sched_event *event)
 {
 	spinlock_init(&event->lock);
-	event->set = false;
+	event->nqueued = 0;
 	event->waiting_thread = NULL;
 }
 
@@ -20,7 +20,7 @@ void reset_event(struct sched_event *event)
 	uint64_t rflag;
 
 	spinlock_irqsave_obtain(&event->lock, &rflag);
-	event->set = false;
+	event->nqueued = 0;
 	event->waiting_thread = NULL;
 	spinlock_irqrestore_release(&event->lock, rflag);
 }
@@ -33,13 +33,13 @@ void wait_event(struct sched_event *event)
 	spinlock_irqsave_obtain(&event->lock, &rflag);
 	ASSERT((event->waiting_thread == NULL), "only support exclusive waiting");
 	event->waiting_thread = sched_get_current(get_pcpu_id());
-	while (!event->set && (event->waiting_thread != NULL)) {
+	event->nqueued++;
+	while ((event->nqueued > 0) && (event->waiting_thread != NULL)) {
 		sleep_thread(event->waiting_thread);
 		spinlock_irqrestore_release(&event->lock, rflag);
 		schedule();
 		spinlock_irqsave_obtain(&event->lock, &rflag);
 	}
-	event->set = false;
 	event->waiting_thread = NULL;
 	spinlock_irqrestore_release(&event->lock, rflag);
 }
@@ -49,7 +49,7 @@ void signal_event(struct sched_event *event)
 	uint64_t rflag;
 
 	spinlock_irqsave_obtain(&event->lock, &rflag);
-	event->set = true;
+	event->nqueued--;
 	if (event->waiting_thread != NULL) {
 		wake_thread(event->waiting_thread);
 	}
diff --git a/hypervisor/include/common/event.h b/hypervisor/include/common/event.h
index 78430b21e..2aba27b32 100644
--- a/hypervisor/include/common/event.h
+++ b/hypervisor/include/common/event.h
@@ -4,7 +4,7 @@
 
 struct sched_event {
 	spinlock_t lock;
-	bool set;
+	int8_t nqueued;
 	struct thread_object* waiting_thread;
 };