My html styles are in a file my-org.css in ~/orghacks

I need (for various reasons) to inline these styles

I have this code in my init to change the html style

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(defun rusi/load-css()
  "Returns string from css file (hardwired) suitable for inline css"
  (interactive)
  (setq org-export-html-style
    (with-temp-buffer
      (insert "\n<style type=\"text/css\">\n")
      (insert-file-contents (expand-file-name "my-org.css" "~/orghacks"))
      (goto-char (point-max))
      (insert "\n</style>\n")
      (buffer-string))))
(rusi/load-css)
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Now if I edit and save the my-org.css file and then call M-: (rusi/load-css)
it does not work.
Restarting emacs makes it work.
Ive checked that org-export-html-style is actually changed.
However org-mode seems to be keeping some internal copy after first use.
org-reload is not helping here