--- a/xpcom/threads/Scheduler.cpp
+++ b/xpcom/threads/Scheduler.cpp
@@ -472,17 +472,19 @@ SchedulerImpl::CreateQueue(nsIIdlePeriod
 
   RefPtr<SchedulerEventQueue> synchronizedQueue = new SchedulerEventQueue(Move(queue));
 
   prioritized->SetMutexRef(synchronizedQueue->MutexRef());
 
   // Setup "main" thread
   mainThread = new nsThread(WrapNotNull(synchronizedQueue), nsThread::MAIN_THREAD, 0);
 
+#ifndef RELEASE_OR_BETA
   prioritized->SetNextIdleDeadlineRef(mainThread->NextIdleDeadlineRef());
+#endif
 
   mainThread.forget(aThread);
   return synchronizedQueue.forget();
 }
 
 void
 SchedulerImpl::Start()
 {