(defun prefix= (needle haystack)
  (string= needle haystack :end2 (min (length haystack) (length needle))))

(defun https-please (url &rest args)
  ;; http://beta.quicklisp.org/
  (if (prefix= "http://beta.quicklisp.org/" url)
    (setf url (concatenate 'string "https://beta.quicklisp.org:443/"
                           (subseq url 26))))
  (print `(fetching ,url))
  (apply #'ql-http:http-fetch url args))

(setf ql-http:*fetch-scheme-functions* '(("http" . https-please)))