diff --git a/scrapy/core/downloader/__init__.py b/scrapy/core/downloader/__init__.py
index b4768f5a9..34fedd427 100644
--- a/scrapy/core/downloader/__init__.py
+++ b/scrapy/core/downloader/__init__.py
@@ -40,6 +40,10 @@ class Slot(object):
 
 def _get_concurrency_delay(concurrency, spider, settings):
     delay = settings.getfloat('DOWNLOAD_DELAY')
+    if hasattr(spider, 'DOWNLOAD_DELAY'):
+        warnings.warn("%s.DOWNLOAD_DELAY attribute is deprecated, use %s.download_delay instead" %
+            (type(spider).__name__, type(spider).__name__))
+        delay = spider.DOWNLOAD_DELAY
     if hasattr(spider, 'download_delay'):
         delay = spider.download_delay