diff --git a/tox.ini b/tox.ini
index c4b6d15c96..e283571afa 100644
--- a/tox.ini
+++ b/tox.ini
@@ -33,7 +33,7 @@ commands =
 
 [testenv:py27]
 commands = {[testenv]commands}
-           ostestr --slowest --serial
+           ostestr {posargs} --slowest --serial
 
 [py3base]
 commands = ostestr --slowest --blacklist-file=blacklist-py3.txt --serial --regex '.*'