diff --git a/tox.ini b/tox.ini
index 9ea1e81..8685a9e 100644
--- a/tox.ini
+++ b/tox.ini
@@ -19,7 +19,7 @@ deps = coverage
   pytest
   pytest-freezegun
   pytest-cov
-  mock
+  mock<4
   httmock
   lxml