diff --git a/tox.ini b/tox.ini
index fe8a7153b..eee78a5c5 100644
--- a/tox.ini
+++ b/tox.ini
@@ -63,6 +63,7 @@ deps =
   pytest-freezegun
   ldaptools>=0.15
   oldldap: python-ldap<3
+  dj18: django-model-utils<3.2
 commands =
   ./getlasso.sh
   rbac,authentic: py.test {env:FAST:} {env:REUSEDB:} {env:COVERAGE:} {env:JUNIT:} {posargs:{env:TESTS} --random-group}