Tag inside other does not work

[sggonzalezg]

Hi, I can't put a tag inside the tag

Example
<h2 class="trn">Lorem Ipsum <span class="trn">dolor sit amet.</span></h2>

This is the output
<h2 class="trn" data-trn-key="<span class="trn">Lorem Ipsum</span> dolor sit amet."><span class="trn">Lorem Ipsum </span>dolor sit amet.</h2>

how can I fix this?