diff --git a/modoboa/lib/tests/__init__.py b/modoboa/lib/tests/__init__.py
index e1f202f0d..f5fa3172f 100644
--- a/modoboa/lib/tests/__init__.py
+++ b/modoboa/lib/tests/__init__.py
@@ -232,6 +232,8 @@ class ModoTestCase(ParametersMixin, TestCase):
 class ModoAPITestCase(ParametersMixin, APITestCase):
     """All test cases must inherit from this one."""
 
+    databases = "__all__"
+
     @classmethod
     def setUpTestData(cls):  # noqa
         """Create a default user."""