diff --git a/doc/go1.21.html b/doc/go1.21.html
index f0fe16bb18..b7686d3fb8 100644
--- a/doc/go1.21.html
+++ b/doc/go1.21.html
@@ -933,7 +933,7 @@ Do not send CLs removing the interior tags from such phrases.
       The <a href="/pkg/syscall#UTF16ToString"><code>UTF16ToString</code></a>
       and <a href="/pkg/syscall#UTF16FromString"><code>UTF16FromString</code></a>
       functions now convert between UTF-16 data and
-      <a href=http://simonsapin.github.io/wtf-8/"">WTF-8</a> strings.
+      <a href="https://simonsapin.github.io/wtf-8/">WTF-8</a> strings.
       This is backward compatible as WTF-8 is a superset of the UTF-8
       format that was used in earlier releases.
     </p>