Post-Purchase Extension not rendering when cart total equals 0

[SimRai32]

As the title mentions when I try to render the post-purchase extension it only works if the total of my cart is greater than 0, however I need it to work when it is equal to 0 as well. Is there any other extension that would work post purchase, but also render when the price is equal to 0, or is there a work around with the post-purchase extension?