diff --git a/tox.ini b/tox.ini
index 4b5b83ffb4..a4967fe1eb 100644
--- a/tox.ini
+++ b/tox.ini
@@ -126,6 +126,7 @@ max-complexity=24
 
 [testenv:docs]
 deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
   .[ldap,memcache,mongodb]
 commands=