diff --git a/tox.ini b/tox.ini
index 439b175..82def82 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,6 +3,7 @@ distribute = False
 envlist = py33,py34,py26,py27,pep8
 
 [testenv]
+install_command = pip install -U {opts} {packages}
 setenv = VIRTUAL_ENV={envdir}
 deps = -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt