diff --git a/designate/tests/unit/test_central/test_basic.py b/designate/tests/unit/test_central/test_basic.py
index 56420ae15..8c487f500 100644
--- a/designate/tests/unit/test_central/test_basic.py
+++ b/designate/tests/unit/test_central/test_basic.py
@@ -313,7 +313,8 @@ class CentralServiceTestCase(CentralBasic):
         self.assertTrue(designate.central.service.storage.get_storage.called)
 
     def test__is_valid_ttl(self):
-        self.CONF.set_override('min_ttl', 10, 'service:central')
+        self.CONF.set_override('min_ttl', 10, 'service:central',
+                               enforce_type=True)
         self.service._is_valid_ttl(self.context, 20)
 
         # policy.check() not to raise: the user is allowed to create low TTLs