the property of xlink for tag tref can not work normally in the Svg module

[blkcor]

code:

<?xml version="1.0" standalone="no"?>
<svg width="400" height="400" xmlns="http://www.w3.org/2000/svg" version="2.0">
  <text id="example" x="100" y="100">This is an example text.</text>

<text>
    <tref xlink:href="#example" />
</text>

</svg>

open with chrome:

This page contains the following errors: error on line 6 at column 33: Namespace prefix xlink for href on tref is not defined

the tref seems work with error