diff --git a/tox.ini b/tox.ini
index 1a9cb2c..5efcc43 100644
--- a/tox.ini
+++ b/tox.ini
@@ -24,7 +24,7 @@ deps =
   djangorestframework>=3.3,<3.8
   pylint
   astroid
-  mock
+  mock<4
   psycopg2-binary
 commands =
   py.test {env:COVERAGE:} {posargs:tests/}