diff --git a/scrapy/contrib/pipeline/images.py b/scrapy/contrib/pipeline/images.py
index 238961ad8..a103d5bd9 100644
--- a/scrapy/contrib/pipeline/images.py
+++ b/scrapy/contrib/pipeline/images.py
@@ -148,9 +148,9 @@ class ImagesPipeline(MediaPipeline):
             's3': S3ImagesStore,
             }
 
-    def __init__(self, store_uri):
+    def __init__(self, store_uri, download_func=None):
         self.store = self._get_store(store_uri)
-        super(ImagesPipeline, self).__init__()
+        super(ImagesPipeline, self).__init__(download_func=download_func)
 
     @classmethod
     def from_settings(cls, settings):
diff --git a/scrapy/tests/test_pipeline_images.py b/scrapy/tests/test_pipeline_images.py
index 95dfa1a0c..41e9be71f 100644
--- a/scrapy/tests/test_pipeline_images.py
+++ b/scrapy/tests/test_pipeline_images.py
@@ -5,8 +5,6 @@ from shutil import rmtree
 
 from twisted.trial import unittest
 
-from scrapy.crawler import Crawler
-from scrapy.conf import settings
 
 try:
     import Image
@@ -14,6 +12,10 @@ try:
 except ImportError, e:
     skip = True
 
+def _mocked_download_func(request, info):
+    response = request.meta.get('response')
+    return response() if callable(response) else response
+
 
 class ImagesPipelineTestCase(unittest.TestCase):
 
@@ -21,14 +23,10 @@ class ImagesPipelineTestCase(unittest.TestCase):
 
     def setUp(self):
         from scrapy.contrib.pipeline.images import ImagesPipeline
-
-        self.crawler = Crawler(settings)
-        self.crawler.install()
         self.tempdir = mkdtemp()
-        self.pipeline = ImagesPipeline(self.tempdir)
+        self.pipeline = ImagesPipeline(self.tempdir, download_func=_mocked_download_func)
 
     def tearDown(self):
-        self.crawler.uninstall()
         rmtree(self.tempdir)
 
     def test_image_path(self):
diff --git a/scrapy/tests/test_pipeline_media.py b/scrapy/tests/test_pipeline_media.py
index 64b506820..569dc2d5b 100644
--- a/scrapy/tests/test_pipeline_media.py
+++ b/scrapy/tests/test_pipeline_media.py
@@ -9,6 +9,8 @@ from scrapy.spider import BaseSpider
 from scrapy.utils.request import request_fingerprint
 from scrapy.contrib.pipeline.media import MediaPipeline
 from scrapy.utils.test import get_crawler
+from scrapy.utils.signal import disconnect_all
+from scrapy import signals
 from scrapy import log
 
 
@@ -28,6 +30,9 @@ class BaseMediaPipelineTestCase(unittest.TestCase):
         self.info = self.pipe.spiderinfo[self.spider]
 
     def tearDown(self):
+        for name, signal in vars(signals).items():
+            if not name.startswith('_'):
+                disconnect_all(signal)
         self.pipe.close_spider(self.spider)
 
     def test_default_media_to_download(self):