1 files changed, 5 insertions, 0 deletions
diff --git a/synapse/handlers/oidc.py b/synapse/handlers/oidc.py
index 45514be50f..1c4a43be0a 100644
--- a/synapse/handlers/oidc.py
+++ b/synapse/handlers/oidc.py
@@ -957,6 +957,11 @@ class OidcProvider:
                 # and attempt to match it.
                 attributes = await oidc_response_to_user_attributes(failures=0)
 
+                if attributes.localpart is None:
+                    # If no localpart is returned then we will generate one, so
+                    # there is no need to search for existing users.
+                    return None
+
                 user_id = UserID(attributes.localpart, self._server_name).to_string()
                 users = await self._store.get_users_by_id_case_insensitive(user_id)
                 if users: