diff --git a/scrapy/trunk/scrapy/conf/default_settings.py b/scrapy/trunk/scrapy/conf/default_settings.py
index 4bf2aa07f..6febc6d4b 100644
--- a/scrapy/trunk/scrapy/conf/default_settings.py
+++ b/scrapy/trunk/scrapy/conf/default_settings.py
@@ -148,6 +148,11 @@ RETRY_HTTP_CODES = ['500', '503', '504', '400', '408', '200']
 ROBOTSTXT_OBEY = False
 
 SCHEDULER = 'scrapy.core.scheduler.Scheduler'
+
+SCHEDULER_MIDDLEWARES = [
+        'scrapy.contrib.schedulermiddleware.duplicatesfilter.DuplicatesFilterMiddleware',
+        ]
+
 SCHEDULER_ORDER = 'BFO'   # available orders: BFO (default), DFO
 
 SPIDER_MODULES = []
diff --git a/scrapy/trunk/scrapy/contrib/downloadermiddleware/redirect.py b/scrapy/trunk/scrapy/contrib/downloadermiddleware/redirect.py
index 767a3cbb2..8de57a1db 100644
--- a/scrapy/trunk/scrapy/contrib/downloadermiddleware/redirect.py
+++ b/scrapy/trunk/scrapy/contrib/downloadermiddleware/redirect.py
@@ -42,13 +42,12 @@ class RedirectMiddleware(object):
         interval, url = get_meta_refresh(response)
         if url and int(interval) < META_REFRESH_MAXSEC:
             redirected = request.replace(url=urljoin(request.url, url))
-            return self._redirect(redirected, request, spider, 'meta refresh') or response
+            return self._redirect(redirected, request, spider, 'meta refresh')
 
         return response
 
     def _redirect(self, redirected, request, spider, reason):
         domain = spider.domain_name
-        if duplicatesfilter.add(domain, redirected) or redirected.dont_filter:
-            log.msg("Redirecting (%s) to %s from %s" % (reason, redirected, request), level=log.DEBUG, domain=domain)
-            return redirected
+        log.msg("Redirecting (%s) to %s from %s" % (reason, redirected, request), level=log.DEBUG, domain=domain)
+        return redirected
 
diff --git a/scrapy/trunk/scrapy/contrib/spidermiddleware/duplicatesfilter.py b/scrapy/trunk/scrapy/contrib/spidermiddleware/duplicatesfilter.py
index eec2dbd86..f327190a9 100644
--- a/scrapy/trunk/scrapy/contrib/spidermiddleware/duplicatesfilter.py
+++ b/scrapy/trunk/scrapy/contrib/spidermiddleware/duplicatesfilter.py
@@ -11,15 +11,12 @@ from scrapy import log
 class DuplicatesFilterMiddleware(object):
     """Filter out already seen requests to avoid visiting pages more than once."""
 
-    def process_spider_input(self, response, spider):
-        duplicatesfilter.add(spider.domain_name, response.request)
-
     def process_spider_output(self, response, result, spider):
         domain = spider.domain_name
         for req in result:
             if isinstance(req, Request):
-                added = duplicatesfilter.add(domain, req)
-                if not (added or req.dont_filter):
+                has = duplicatesfilter.has(domain, req)
+                if has and not req.dont_filter:
                     log.msg('Skipped (already processed): %s' % req, log.TRACE, domain=domain)
                     continue
             yield req
diff --git a/scrapy/trunk/scrapy/core/engine.py b/scrapy/trunk/scrapy/core/engine.py
index 96165f5b5..d4b058427 100644
--- a/scrapy/trunk/scrapy/core/engine.py
+++ b/scrapy/trunk/scrapy/core/engine.py
@@ -14,7 +14,7 @@ from scrapy import log
 from scrapy.stats import stats
 from scrapy.conf import settings
 from scrapy.core import signals
-from scrapy.core.scheduler import Scheduler
+from scrapy.core.scheduler import Scheduler, SchedulerMiddlewareManager
 from scrapy.core.downloader import Downloader
 from scrapy.core.exceptions import IgnoreRequest, HttpException, DontCloseDomain
 from scrapy.http import Response, Request
@@ -59,6 +59,7 @@ class ExecutionEngine(object):
         Configure execution engine with the given scheduling policy and downloader.
         """
         self.scheduler = scheduler or Scheduler()
+        self.schedulermiddleware = SchedulerMiddlewareManager(self.scheduler)
         self.downloader = downloader or Downloader(self)
         self.spidermiddleware = SpiderMiddlewareManager()
         self._scraping = {}
@@ -299,7 +300,7 @@ class ExecutionEngine(object):
             return self._add_starter(request, spider, domain_priority)
         if self.debug_mode: 
             log.msg('Scheduling %s (now)' % request_info(request), log.DEBUG)
-        schd = self.scheduler.enqueue_request(domain, request, priority)
+        schd = self.schedulermiddleware.enqueue_request(domain, request, priority)
         self.next_request(spider)
         return schd
 
diff --git a/scrapy/trunk/scrapy/core/scheduler/__init__.py b/scrapy/trunk/scrapy/core/scheduler/__init__.py
index 35ed94303..51f8ecab5 100644
--- a/scrapy/trunk/scrapy/core/scheduler/__init__.py
+++ b/scrapy/trunk/scrapy/core/scheduler/__init__.py
@@ -1,2 +1,3 @@
 from scrapy.core.scheduler.schedulers import Scheduler
 from scrapy.core.scheduler.store import MemoryStore
+from scrapy.core.scheduler.middleware import SchedulerMiddlewareManager
diff --git a/scrapy/trunk/scrapy/tests/test_spidermiddleware_duplicatesfilter.py b/scrapy/trunk/scrapy/tests/test_spidermiddleware_duplicatesfilter.py
index 2d6ef03b0..a9e405440 100644
--- a/scrapy/trunk/scrapy/tests/test_spidermiddleware_duplicatesfilter.py
+++ b/scrapy/trunk/scrapy/tests/test_spidermiddleware_duplicatesfilter.py
@@ -14,6 +14,9 @@ class DuplicatesFilterMiddlewareTest(unittest.TestCase):
         self.spider = spiders.fromdomain('scrapytest.org')
         duplicatesfilter.open('scrapytest.org')
 
+    def tearDown(self):
+        duplicatesfilter.close('scrapytest.org')
+
     def test_process_spider_output(self):
         mw = DuplicatesFilterMiddleware()
 
@@ -25,10 +28,12 @@ class DuplicatesFilterMiddlewareTest(unittest.TestCase):
         r2 = Request('http://scrapytest.org/2')
         r3 = Request('http://scrapytest.org/2')
 
-        mw.process_spider_input(response, self.spider)
+        duplicatesfilter.add('scrapytest.org', r0)
+        duplicatesfilter.add('scrapytest.org', r2)
+
         filtered = list(mw.process_spider_output(response, [r0, r1, r2, r3], self.spider))
 
         assert r0 not in filtered
         assert r1 in filtered
-        assert r2 in filtered
+        assert r2 not in filtered
         assert r3 not in filtered