diff --git a/jupyterhub/handlers/base.py b/jupyterhub/handlers/base.py
index c1685686..5c7e4a75 100644
--- a/jupyterhub/handlers/base.py
+++ b/jupyterhub/handlers/base.py
@@ -856,7 +856,7 @@ class BaseHandler(RequestHandler):
 
         if server_name:
             if '/' in server_name:
-                error_message = f"Invalid server_name: {server_name}"
+                error_message = f"Invalid server_name (may not contain '/'): {server_name}"
                 self.log.error(error_message)
                 raise web.HTTPError(400, error_message)
             user_server_name = f'{user.name}:{server_name}'
diff --git a/jupyterhub/user.py b/jupyterhub/user.py
index 9fd29809..bf091a13 100644
--- a/jupyterhub/user.py
+++ b/jupyterhub/user.py
@@ -687,7 +687,6 @@ class User:
                 client_id,
                 api_token,
                 url_path_join(self.url, url_escape_path(server_name), 'oauth_callback'),
-                # url_path_join(self.url, server_name, 'oauth_callback'),
                 allowed_roles=allowed_roles,
                 description="Server at %s"
                 % (url_path_join(self.base_url, server_name) + '/'),