diff --git a/scrapy/contrib/downloadermiddleware/downloadtimeout.py b/scrapy/contrib/downloadermiddleware/downloadtimeout.py
index 612b081ec..18123cfce 100644
--- a/scrapy/contrib/downloadermiddleware/downloadtimeout.py
+++ b/scrapy/contrib/downloadermiddleware/downloadtimeout.py
@@ -14,7 +14,7 @@ class DownloadTimeoutMiddleware(object):
 
     @classmethod
     def from_crawler(cls, crawler):
-        o = cls(crawler.settings['DOWNLOAD_TIMEOUT'])
+        o = cls(crawler.settings.getfloat('DOWNLOAD_TIMEOUT'))
         crawler.signals.connect(o.spider_opened, signal=signals.spider_opened)
         return o
 
diff --git a/tests/test_downloadermiddleware_downloadtimeout.py b/tests/test_downloadermiddleware_downloadtimeout.py
index 3e3ff2401..aba06686a 100644
--- a/tests/test_downloadermiddleware_downloadtimeout.py
+++ b/tests/test_downloadermiddleware_downloadtimeout.py
@@ -8,8 +8,8 @@ from scrapy.utils.test import get_crawler
 
 class DownloadTimeoutMiddlewareTest(unittest.TestCase):
 
-    def get_request_spider_mw(self):
-        crawler = get_crawler(Spider)
+    def get_request_spider_mw(self, settings=None):
+        crawler = get_crawler(Spider, settings)
         spider = crawler._create_spider('foo')
         request = Request('http://scrapytest.org/')
         return request, spider, DownloadTimeoutMiddleware.from_crawler(crawler)
@@ -20,6 +20,12 @@ class DownloadTimeoutMiddlewareTest(unittest.TestCase):
         assert mw.process_request(req, spider) is None
         self.assertEquals(req.meta.get('download_timeout'), 180)
 
+    def test_string_download_timeout(self):
+        req, spider, mw = self.get_request_spider_mw({'DOWNLOAD_TIMEOUT': '20.1'})
+        mw.spider_opened(spider)
+        assert mw.process_request(req, spider) is None
+        self.assertEquals(req.meta.get('download_timeout'), 20.1)
+
     def test_spider_has_download_timeout(self):
         req, spider, mw = self.get_request_spider_mw()
         spider.download_timeout = 2