diff --git a/tox.ini b/tox.ini
index 7c538df073..47b30f6c30 100644
--- a/tox.ini
+++ b/tox.ini
@@ -21,15 +21,15 @@ commands =
   bash tools/pretty_tox.sh '{posargs}'
 
 [testenv:debug]
-commands = oslo_debug_helper {posargs}
+commands = oslo_debug_helper -t magnum/tests/unit {posargs}
 
 [testenv:debug-py27]
 basepython = python2.7
-commands = oslo_debug_helper {posargs}
+commands = oslo_debug_helper -t magnum/tests/unit {posargs}
 
 [testenv:debug-py35]
 basepython = python3.5
-commands = oslo_debug_helper {posargs}
+commands = oslo_debug_helper -t magnum/tests/unit {posargs}
 
 [testenv:functional-api]
 sitepackages = True