diff --git a/lisp/term/sun.el b/lisp/term/sun.el
index 52373c4ccd3..c5ee5c94509 100644
--- a/lisp/term/sun.el
+++ b/lisp/term/sun.el
@@ -98,8 +98,8 @@
 (defvar sun-esc-bracket nil
   "*If non-nil, rebind ESC [ as prefix for Sun function keys.")
 
-(define-prefix-command 'sun-raw-prefix)
-(define-key function-key-map "\e[" 'sun-raw-prefix)
+(defvar sun-raw-prefix (make-sparse-keymap))
+(define-key function-key-map "\e[" sun-raw-prefix)
 
 (define-key sun-raw-prefix "210z" [r3])
 (define-key sun-raw-prefix "213z" [r6])