diff --git a/extras/build_release.sh b/extras/build_release.sh
index 57873b12e..2230685e8 100755
--- a/extras/build_release.sh
+++ b/extras/build_release.sh
@@ -6,8 +6,8 @@
 hg purge --all
 
 # build packages
-version=$(python -c "import scrapy; print scrapy.__version__")
-python setup.py sdist
+#version=$(python -c "import scrapy; print scrapy.__version__")
+#python setup.py sdist
 # FIXME: bdist_wininst doesn't work on Unix (it doesn't include the data_files)
 # To build the win32 release you need to use Windows for now.
 #python setup.py bdist_wininst -t "Scrapy $version" -p "win32"
diff --git a/scrapy/__init__.py b/scrapy/__init__.py
index bee059b0b..5e206de2f 100644
--- a/scrapy/__init__.py
+++ b/scrapy/__init__.py
@@ -3,8 +3,8 @@ Scrapy - a screen scraping framework written in Python
 """
 
 # IMPORTANT: remember to also update the version in docs/conf.py
-version_info = (0, 7, 0, 'final', 0)
-__version__ = "0.7"
+version_info = (0, 8, 0, '', 0)
+__version__ = "0.8-dev"
 
 import sys, os
 
diff --git a/scrapy/core/engine.py b/scrapy/core/engine.py
index 004a65b98..6f1352d6a 100644
--- a/scrapy/core/engine.py
+++ b/scrapy/core/engine.py
@@ -228,6 +228,9 @@ class ExecutionEngine(object):
             self.next_request(spider)
             return _
 
+        if spider not in self.downloader.sites:
+            return defer.fail(Failure(IgnoreRequest())).addBoth(_on_complete)
+
         dwld = mustbe_deferred(self.downloader.fetch, request, spider)
         dwld.addCallbacks(_on_success, _on_error)
         dwld.addBoth(_on_complete)