1 files changed, 7 insertions, 0 deletions
diff --git a/tests/handlers/test_register.py b/tests/handlers/test_register.py
index 1c253d0579..5ffba2ca7a 100644
--- a/tests/handlers/test_register.py
+++ b/tests/handlers/test_register.py
@@ -228,3 +228,10 @@ class RegistrationTestCase(unittest.HomeserverTestCase):
     def test_register_not_support_user(self):
         res = self.get_success(self.handler.register(localpart='user'))
         self.assertFalse(self.store.is_support_user(res[0]))
+
+    def test_invalid_user_id_length(self):
+        invalid_user_id = "x" * 256
+        self.get_failure(
+            self.handler.register(localpart=invalid_user_id),
+            SynapseError
+        )