diff --git a/lisp/language/korea-util.el b/lisp/language/korea-util.el
index da91e692719..cca702f71b0 100644
--- a/lisp/language/korea-util.el
+++ b/lisp/language/korea-util.el
@@ -27,13 +27,22 @@
 
 ;;; Code:
 
+(defgroup korean nil
+  "Options for writing Korean."
+  :version "31.1"
+  :group 'languages)
+
 ;;;###autoload
-(defvar default-korean-keyboard
+(defcustom default-korean-keyboard
   (if (string-search "3" (or (getenv "HANGUL_KEYBOARD_TYPE") ""))
       "3"
     "")
   "The kind of Korean keyboard for Korean (Hangul) input method.
-\"\" for 2, \"3\" for 3, and \"3f\" for 3f.")
+\"\" for 2, \"3\" for 3, and \"3f\" for 3f."
+  :initialize #'custom-initialize-delay
+  :group 'korean
+  :version "31.1"
+  :type 'string)
 
 ;; functions useful for Korean text input