How to print white text on a black background

Hello all, I hope you can help me.

I'm currently using BarTender to create a label template I intend to print on a Zebra ZT610.

The template has a Code 128 barcode which is human visible and it must be printed in white letters atop of a black rectangle (which has a fixed size due to label design).

My problem is that I have not been able to make the white letters of the barcode to be visible on top of the black rectangle. I have used the BarTender properties to make sure the objects are in the correct Z order, I have sent the barcode to the top and the black rectangle to the back and still does not work even though in the print preview the white letters are shown correctly.

I have tried replacing the black rectangle with other objects such as picture or a text box and still does not work. I should also note that if print the template in a non Zebra printer, the label comes out correctly.

I have attached a picture of the barcode in question.

Any help on solving this issue would be greatly appreciated.