diff --git a/tox.ini b/tox.ini
index b8fd6e7..bec51c0 100644
--- a/tox.ini
+++ b/tox.ini
@@ -29,7 +29,7 @@ commands =
 commands = python setup.py build_sphinx
 
 [testenv:debug]
-commands = oslo_debug_helper {posargs}
+commands = oslo_debug_helper -t watcherclient/tests/unit {posargs}
 
 [testenv:functional]
 basepython = python2.7