diff --git a/tox.ini b/tox.ini
index 023f7ea..38a40f2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,7 @@ skipsdist = True
 
 [testenv]
 usedevelop = True
-install_command = pip install -U {opts} {packages}
+install_command = pip install -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt} {opts} {packages}
 setenv =
     VIRTUAL_ENV={envdir}
     DISCOVER_DIRECTORY=kingbird/tests/unit