diff --git a/jupyterhub/tests/mocking.py b/jupyterhub/tests/mocking.py
index e01c1e4b..01bcf909 100644
--- a/jupyterhub/tests/mocking.py
+++ b/jupyterhub/tests/mocking.py
@@ -243,7 +243,8 @@ class MockHub(JupyterHub):
             cert_location = kwargs['internal_certs_location']
             kwargs['external_certs'] = ssl_setup(cert_location, 'hub-ca')
         super().__init__(*args, **kwargs)
-        self.config.Authenticator.allow_all = True
+        if 'allow_all' not in self.config.Authenticator:
+            self.config.Authenticatorallow_all = True
 
     @default('subdomain_host')
     def _subdomain_host_default(self):
diff --git a/jupyterhub/tests/test_app.py b/jupyterhub/tests/test_app.py
index 9a3f0e2a..819a00e6 100644
--- a/jupyterhub/tests/test_app.py
+++ b/jupyterhub/tests/test_app.py
@@ -475,6 +475,7 @@ async def test_user_creation(tmpdir, request):
     ]
 
     cfg = Config()
+    cfg.Authenticator.allow_all = False
     cfg.Authenticator.allowed_users = allowed_users
     cfg.JupyterHub.load_groups = groups
     cfg.JupyterHub.load_roles = roles