diff --git a/tox.ini b/tox.ini
index a265485..4adf2f7 100644
--- a/tox.ini
+++ b/tox.ini
@@ -4,7 +4,7 @@ distribute = False
 envlist = py35,py27,pep8
 
 [testenv]
-install_command = pip install -U {opts} {packages}
+install_command = pip install {opts} {packages}
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
   -r{toxinidir}/test-requirements.txt