diff --git a/tox.ini b/tox.ini
index c2d1683..2fbf078 100644
--- a/tox.ini
+++ b/tox.ini
@@ -35,7 +35,7 @@ deps =
   pytest-django
   pytest>=3.3.0
   WebTest
-  mock
+  mock<4
   httmock
   psycopg2-binary
   pylint<1.8