Index: include-fixer/tool/clang-include-fixer.el
===================================================================
--- include-fixer/tool/clang-include-fixer.el
+++ include-fixer/tool/clang-include-fixer.el
@@ -187,9 +187,9 @@
   "Replace current buffer by content of STDOUT."
   (cl-check-type stdout buffer-live)
   (barf-if-buffer-read-only)
-  (unless (clang-include-fixer--insert-line stdout (current-buffer))
-    (erase-buffer)
-    (insert-buffer-substring stdout))
+  (cond ((fboundp 'replace-buffer-contents) (replace-buffer-contents stdout))
+        ((clang-include-fixer--insert-line stdout (current-buffer)))
+        (t (erase-buffer) (insert-buffer-substring stdout)))
   (message "Fix applied")
   nil)