diff --git a/scrapy/core/engine.py b/scrapy/core/engine.py
index 6731c59b7..6d68d0a27 100644
--- a/scrapy/core/engine.py
+++ b/scrapy/core/engine.py
@@ -121,7 +121,7 @@ class ExecutionEngine(object):
         while not self._needs_backout(spider) and slot.start_requests:
             try:
                 request = next(slot.start_requests)
-                if request == signals.WaitUntilQueueEmpty:
+                if request == spider.WaitUntilQueueEmpty:
                     break
                 self.crawl(request, spider)
 
diff --git a/scrapy/signals.py b/scrapy/signals.py
index fe724ce80..de0886fb6 100644
--- a/scrapy/signals.py
+++ b/scrapy/signals.py
@@ -26,5 +26,3 @@ stats_spider_closed = spider_closed
 item_passed = item_scraped
 
 request_received = request_scheduled
-
-WaitUntilQueueEmpty = object()
diff --git a/scrapy/spiders/__init__.py b/scrapy/spiders/__init__.py
index 4e214ec16..80a36cf6d 100644
--- a/scrapy/spiders/__init__.py
+++ b/scrapy/spiders/__init__.py
@@ -17,6 +17,8 @@ from scrapy.utils.python import iflatten
 
 
 class Spider(object_ref):
+    WaitUntilQueueEmpty = object()
+
     """Base class for scrapy spiders. All spiders must inherit from this
     class.
     """
@@ -84,7 +86,7 @@ class Spider(object_ref):
                 yield Request(url, dont_filter=True)
 
     def start_requests_with_control(self):
-        sig = signals.WaitUntilQueueEmpty
+        sig = self.WaitUntilQueueEmpty
         gen_ = ((r, sig) if r != sig else (r,) for r in self.start_requests())
         return iflatten(gen_)