diff --git a/lisp/textmodes/toml-ts-mode.el b/lisp/textmodes/toml-ts-mode.el
index 2c491034372..193c83f9aec 100644
--- a/lisp/textmodes/toml-ts-mode.el
+++ b/lisp/textmodes/toml-ts-mode.el
@@ -39,8 +39,8 @@
 (defcustom toml-ts-mode-indent-offset 2
   "Number of spaces for each indentation step in `toml-ts-mode'."
   :version "29.1"
-  :type 'integer
-  :safe 'integerp
+  :type 'natnum
+  :safe 'natnump
   :group 'toml)
 
 (defvar toml-ts-mode--syntax-table