diff --git a/tox.ini b/tox.ini
index ffe3f28..bfd004a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -16,7 +16,7 @@ deps =
   pytest-django
   pytest
   WebTest
-  mock
+  mock<4
   httmock
   requests-mock
   ipdb