diff --git a/tox.ini b/tox.ini
index bd9e5d6aa..64b60327e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -11,6 +11,7 @@ envlist =
 commands = ./runtests.py --fast {posargs} --coverage -rw
 setenv =
        PYTHONDONTWRITEBYTECODE=1
+       PYTHONWARNINGS=once
 deps =
         django17: Django==1.7.11
         django18: Django==1.8.9