 		if isFunction onRejected
 			p2._onRejected = onRejected
 
-		p2._pre = p1
+		p2._pre = p1 if isLongStackTrace
 		p1[p1._pCount++] = p2
 
 		# 2.2.6


	# iter tree
	hashOnRejected = (node) ->
		i = 0
		len = node._pCount


	# Why are there two "genScheduler"s?
	# Well, to support the babel's es7 async-await polyfill, I have to hack it.
	scheduleUnhandledRejection = genScheduler 9, (genScheduler 9, (p) ->
		if not hashOnRejected p
			Yaku.onUnhandledRejection p._value, p

		return
	)
