diff --git a/lisp/json.el b/lisp/json.el
index eb655162d3..461f688f9c 100644
--- a/lisp/json.el
+++ b/lisp/json.el
@@ -199,6 +199,8 @@ json--with-output-to-string
      (with-current-buffer standard-output
        ;; This affords decent performance gains.
        (setq-local inhibit-modification-hooks t)
+       ;; Ignore `read-only' property once and for all (bug#43549).
+       (setq-local inhibit-read-only t)
        ,@body)))
 
 (defmacro json--with-indentation (&rest body)
@@ -458,9 +460,9 @@ json-read-string
 (defun json--print-string (string &optional from)
   "Insert a JSON representation of STRING at point.
 FROM is the index of STRING to start from and defaults to 0."
-  (goto-char (prog1 (1+ (point))
-               ;; Strip `read-only' property (bug#43549).
-               (insert ?\" (substring-no-properties string from))))
+  (goto-char (prog1 (1+ (point)) (insert ?\" string)))
+  (set-text-properties (point) (point-max) ())
+  (and from (delete-char from))
   ;; Escape only quotation mark, backslash, and the control
   ;; characters U+0000 to U+001F (RFC 4627, ECMA-404).
   (while (re-search-forward (rx (in ?\" ?\\ cntrl)) nil 'move)