diff --git a/tox.ini b/tox.ini
index 04497af16e..55b227b65c 100644
--- a/tox.ini
+++ b/tox.ini
@@ -12,7 +12,6 @@ setenv = VIRTUAL_ENV={envdir}
          LANGUAGE=en_US
          LC_ALL=en_US.UTF-8
          PYTHONWARNINGS=default::DeprecationWarning
-         TESTS_DIR=./ironic/tests/unit/
 deps =
   -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
   -r{toxinidir}/requirements.txt