diff --git a/tox.ini b/tox.ini
index e5698d2..9389cf4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -9,6 +9,7 @@
          LANGUAGE=en_US:en
          LC_ALL=C
 usedevelop = True
+install_command = pip install -U {opts} {packages}
 
 [testenv:py26]
 commands = python setup.py test --slowest --testr-arg='tempest\.tests {posargs}'