diff --git a/url-encode.lisp b/url-encode.lisp
index e471d38..d11aa2e 100644
--- a/url-encode.lisp
+++ b/url-encode.lisp
@@ -1,4 +1,7 @@
 (in-package :cl-xdg-trash/url-encode)
+;; Some useful links
+;; https://en.wikipedia.org/wiki/UTF-8
+;; https://en.wikipedia.org/wiki/Percent-encoding
 
 (declaim (ftype (function (character) t) url-unreserved-character-p))
 (defun url-unreserved-character-p (char)
@@ -18,7 +21,7 @@
 
 (deftype utf-8-char ()
   '(or
-    (cons (integer 0 #b1010111) null)
+    (cons (integer 0 #b1111111) null)
 
     (cons (integer #b11000000 #b11011111) (cons utf-8-middle-byte null))