diff --git a/scrapy/core/downloader/__init__.py b/scrapy/core/downloader/__init__.py
index 157dc3418..5a2fdadf5 100644
--- a/scrapy/core/downloader/__init__.py
+++ b/scrapy/core/downloader/__init__.py
@@ -181,6 +181,9 @@ class Downloader(object):
         def finish_transferring(_):
             slot.transferring.remove(request)
             self._process_queue(spider, slot)
+            self.signals.send_catch_log(signal=signals.request_left_downloader,
+                                        request=request,
+                                        spider=spider)
             return _
 
         return dfd.addBoth(finish_transferring)