1 files changed, 1 insertions, 0 deletions

diff --git a/lisp/emacs-lisp/disass.el b/lisp/emacs-lisp/disass.el
index c23dbe1e068..82c8de6e133 100644
--- a/lisp/emacs-lisp/disass.el
+++ b/lisp/emacs-lisp/disass.el
@@ -103,6 +103,7 @@ redefine OBJECT if it is a symbol."
               (when (re-search-forward "^.*<.*>:" nil t 2)
                 (delete-region (match-beginning 0) (point-max)))
               (asm-mode)
+              (setq buffer-read-only t)
               (cl-return-from disassemble-internal))
           (error "Can't disassemble #<subr %s>" name)))
     (if (eq (car-safe obj) 'macro)      ;Handle macros.