diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index b60827fa..c86c6d3e 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -1888,7 +1888,7 @@ strio_truncate(VALUE self, VALUE len)
  *   external_encoding -> encoding or nil
  *
  * Returns an Encoding object that represents the encoding of the string;
- * see {Encoding}[https://docs.ruby-lang.org/en/master/Encoding.html]:
+ * see {Encodings}[rdoc-ref:StringIO@Encodings]:
  *
  *   strio = StringIO.new('foo')
  *   strio.external_encoding # => #<Encoding:UTF-8>