1 files changed, 8 insertions, 0 deletions
diff --git a/tests/rest/client/test_profile.py b/tests/rest/client/test_profile.py
index 77c3ced42e..29bed0e872 100644
--- a/tests/rest/client/test_profile.py
+++ b/tests/rest/client/test_profile.py
@@ -13,6 +13,8 @@
 # limitations under the License.
 
 """Tests REST events for /profile paths."""
+import urllib.parse
+from http import HTTPStatus
 from typing import Any, Dict, Optional
 
 from twisted.test.proto_helpers import MemoryReactor
@@ -49,6 +51,12 @@ class ProfileTestCase(unittest.HomeserverTestCase):
         res = self._get_displayname()
         self.assertEqual(res, "owner")
 
+    def test_get_displayname_rejects_bad_username(self) -> None:
+        channel = self.make_request(
+            "GET", f"/profile/{urllib.parse.quote('@alice:')}/displayname"
+        )
+        self.assertEqual(channel.code, HTTPStatus.BAD_REQUEST, channel.result)
+
     def test_set_displayname(self) -> None:
         channel = self.make_request(
             "PUT",