diff --git a/tox.ini b/tox.ini
index b31e3eaa6..b39ab2556 100644
--- a/tox.ini
+++ b/tox.ini
@@ -34,8 +34,8 @@ deps =
 [testenv:trunk]
 basepython = python2.7
 commands =
-    pip install https://github.com/scrapy/w3lib/archive/master.zip#egg=w3lib
-    pip install https://github.com/scrapy/queuelib/archive/master.zip#egg=queuelib
+    pip install -U https://github.com/scrapy/w3lib/archive/master.zip#egg=w3lib
+    pip install -U https://github.com/scrapy/queuelib/archive/master.zip#egg=queuelib
     py.test --twisted {posargs:scrapy}
 
 [testenv:py33]