diff --git a/tox.ini b/tox.ini
index ad3c7765928b..13dd71205ab5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,6 +3,7 @@ skipsdist = True
 envlist = {py27}-{nosetest,pep8}, cover
 
 [testenv]
+passenv = PYTHONPATH
 basepython = 
     cover,py27: python2.7
 deps =