diff --git a/tox.ini b/tox.ini
index 2ec367e..2da2a3a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -34,7 +34,9 @@ commands =
     coverage xml -o cover/coverage.xml
 
 [testenv:docs]
-deps = -r{toxinidir}/doc/requirements.txt
+deps =
+  -c{env:UPPER_CONSTRAINTS_FILE:https://git.openstack.org/cgit/openstack/requirements/plain/upper-constraints.txt}
+  -r{toxinidir}/doc/requirements.txt
 commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:releasenotes]