Browser issue -moz-element being ignored?


Well-known member
I'm currently creating a theme and need to use -moz-element to create a specific effect in Firefox. Use this code as an example:
#test{ background: #5689b9; color: #fff; padding: 5px; }
#test2{ height: 190px; width: 200px; background: -moz-element(#test); margin-top: 10px; }
<div id='test'>This is a test</div>
<div id='test2'></div>
This code works fine in regular HTML files, but seems to be ignored in xenforo.

HTML file:
Screen Shot 2014-06-19 at 11.01.26 am.png

When used in xenforo, the background fails to appear (added to page_container):
Screen Shot 2014-06-19 at 11.01.58 am.png

I have also tried alternatives such as:
background-image: -moz-element(#test); background-repeat: repeat;
..and have also used !important tags to try and force the image, to no avail.

I'm aware that xenforo auto prefixes certain properties, so could that somehow be affecting this code unintentionally?