diff --git a/tox.ini b/tox.ini
index b592ba0..e82d302 100644
--- a/tox.ini
+++ b/tox.ini
@@ -18,7 +18,7 @@ deps =
   dj111: django>=1.11,<1.12
   dj22: django>=2.2,<2.3
   pg: psycopg2
-  mock
+  mock<4
   httmock
   pytest
   pytest-cov