diff --git a/ext/stringio/stringio.c b/ext/stringio/stringio.c
index aaf008ad..cd5edd66 100644
--- a/ext/stringio/stringio.c
+++ b/ext/stringio/stringio.c
@@ -715,7 +715,7 @@ strio_set_lineno(VALUE self, VALUE lineno)
  *   binmode -> self
  *
  * Sets the data mode in +self+ to binary mode;
- * see {Data Mode}[rdoc-ref:File@Data+Mode].
+ * see {Data Mode}[https://docs.ruby-lang.org/en/master/File.html#class-File-label-Data+Mode].
  *
  */
 static VALUE