diff --git a/allauth_cas/views.py b/allauth_cas/views.py
index d2ea9b7..b27b3c7 100644
--- a/allauth_cas/views.py
+++ b/allauth_cas/views.py
@@ -217,7 +217,7 @@ class CASCallbackView(CASView):
         # Keep tracks of the last used CAS provider.
         request.session[CAS_PROVIDER_SESSION_KEY] = self.provider.id
 
-        data = (uid, extra)
+        data = (uid, extra or {})
 
         # Finish the login flow.
         login = self.adapter.complete_login(request, data)
diff --git a/tests/test_views.py b/tests/test_views.py
index ebae670..e7b04e1 100644
--- a/tests/test_views.py
+++ b/tests/test_views.py
@@ -184,7 +184,7 @@ class CASCallbackViewTests(CASViewTestCase):
         self.assertEqual('/accounts/theid/login/callback/', url)
 
     def test_ticket_valid(self):
-        """p(
+        """
         If ticket is valid, the user is logged in.
         """
         self.patch_cas_response(username='username', valid_ticket='123456')
@@ -211,6 +211,18 @@ class CASCallbackViewTests(CASViewTestCase):
         r = self.client.get('/accounts/theid/login/callback/')
         self.assertLoginFailure(r)
 
+    def test_attributes_is_none(self):
+        """
+        Without extra attributes, CASClientV2 of python-cas returns None.
+        """
+        self.patch_cas_response(
+            username='username', valid_ticket='123456', attributes=None
+        )
+        r = self.client.get('/accounts/theid/login/callback/', {
+            'ticket': '123456',
+        })
+        self.assertLoginSuccess(r)
+
 
 class CASLogoutViewTests(CASViewTestCase):