2 files changed, 20 insertions, 19 deletions
diff --git a/lisp/org/org-compat.el b/lisp/org/org-compat.el
index 59d34b661c6..297e8f06045 100644
--- a/lisp/org/org-compat.el
+++ b/lisp/org/org-compat.el
@@ -292,10 +292,20 @@ older than 27.1"
       (if tree (push tree elems))
       (nreverse elems))))
 
-(if (version< emacs-version "27.1")
-    (defsubst org-replace-buffer-contents (source &optional _max-secs _max-costs)
-      (replace-buffer-contents source))
-  (defalias 'org-replace-buffer-contents #'replace-buffer-contents))
+(defalias 'org-replace-region-contents
+  (if (> emacs-major-version 30)
+      #'replace-region-contents
+    ;; The `replace-region-contents' in Emacs<31 does not accept a buffer
+    ;; as SOURCE argument and does not preserve the position well enough.
+    (lambda (beg end source &optional max-secs max-costs)
+      (save-restriction
+        (narrow-to-region beg end)
+        (let ((eobp (eobp)))
+          (with-no-warnings
+            (if (< emacs-major-version 27)
+                (replace-buffer-contents source)
+              (replace-buffer-contents source max-secs max-costs)))
+          (if eobp (goto-char (point-max))))))))
 
 (unless (fboundp 'proper-list-p)
   ;; `proper-list-p' was added in Emacs 27.1.  The function below is
diff --git a/lisp/org/org-src.el b/lisp/org/org-src.el
index 302c27ac866..d8a928b1f9f 100644
--- a/lisp/org/org-src.el
+++ b/lisp/org/org-src.el
@@ -1414,13 +1414,9 @@ EVENT is passed to `mouse-set-point'."
       ;; insert new contents.
       (delete-overlay overlay)
       (let ((expecting-bol (bolp)))
-	(if (version< emacs-version "27.1")
-	    (progn (delete-region beg end)
-		   (insert (with-current-buffer write-back-buf (buffer-string))))
-	  (save-restriction
-	    (narrow-to-region beg end)
-	    (org-replace-buffer-contents write-back-buf 0.1 nil)
-	    (goto-char (point-max))))
+        (goto-char end)
+        (org-replace-region-contents beg end write-back-buf 0.1 nil)
+        (cl-assert (= (point) (+ beg (buffer-size write-back-buf))))
 	(when (and expecting-bol (not (bolp))) (insert "\n")))
       (kill-buffer write-back-buf)
       (save-buffer)
@@ -1461,14 +1457,9 @@ EVENT is passed to `mouse-set-point'."
        (undo-boundary)
        (goto-char beg)
        (let ((expecting-bol (bolp)))
-	 (if (version< emacs-version "27.1")
-	     (progn (delete-region beg end)
-		    (insert (with-current-buffer write-back-buf
-                              (buffer-string))))
-	   (save-restriction
-	     (narrow-to-region beg end)
-	     (org-replace-buffer-contents write-back-buf 0.1 nil)
-	     (goto-char (point-max))))
+         (goto-char end)
+         (org-replace-region-contents beg end write-back-buf 0.1 nil)
+         (cl-assert (= (point) (+ beg (buffer-size write-back-buf))))
 	 (when (and expecting-bol (not (bolp))) (insert "\n")))))
     (when write-back-buf (kill-buffer write-back-buf))
     ;; If we are to return to source buffer, put point at an