diff --git a/tox.ini b/tox.ini
index 4a43d47..11aa1c6 100644
--- a/tox.ini
+++ b/tox.ini
@@ -2,6 +2,7 @@
 envlist = pep8,pypy,py33,py34,py27,py26
 
 [testenv]
+usedevelop = True
 deps =
     nose
     nose-parameterized