diff --git a/tox.ini b/tox.ini
index 9a5c8dff..64fb1175 100644
--- a/tox.ini
+++ b/tox.ini
@@ -82,6 +82,9 @@ commands =
 [testenv:docs]
 deps =
   -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  # magnum-ui doc generated the module reference,
+  # so requirements.txt should be here to apply upper-constraints.
+  -r{toxinidir}/requirements.txt
   -r{toxinidir}/doc/requirements.txt
 commands=
   sphinx-build -W -b html doc/source doc/build/html