diff --git a/tox.ini b/tox.ini
index d4e485ac2..d7db9956b 100644
--- a/tox.ini
+++ b/tox.ini
@@ -56,7 +56,7 @@ deps =
   pytest-cov
   pytest-django
   pytest-random
-  mock
+  mock<4
   pytest!=5.3.3
   lxml
   cssselect