diff --git a/tox.ini b/tox.ini
index d9250dc6..fe80eb7d 100644
--- a/tox.ini
+++ b/tox.ini
@@ -26,7 +26,7 @@ commands = bash -c "find {toxinidir}          \
 
 [testenv:docs]
 deps =
-  -c{env:UPPER_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
+  -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/doc/requirements.txt
 commands =
   rm -rf doc/build