diff --git a/server/router/admin/rust.router.js b/server/router/admin/rust.router.js
index f925ea0..e489978 100644
--- a/server/router/admin/rust.router.js
+++ b/server/router/admin/rust.router.js
@@ -159,8 +159,10 @@ adminRustRouter.put(
   /* #swagger.responses[404] = { description: 'No such server' } */
   requireRole('admin'),
   param('id').isString().isLength({ min: 1, max: 64 }),
-  body('mode').optional().isIn(['first', 'all', 'upto']),
-  body('rules').isArray({ max: 10 }).withMessage('rules is a list of at most ten'),
+  // Shape only. The words, the bounds and the per-rule sentences are
+  // `titles.validateSettings`'s, in the controller, so a bad mode reaches the
+  // form as a sentence rather than as "Invalid value".
+  body('rules').isArray().withMessage('rules is a list'),
   validate,
   admin.putTitles,
 )