Gift Certificate - not calculating correctly

Project:Gift Certificate Module
Component:Code
Category:
Priority:critical
Assigned:Unassigned
Status:active
Description
Project: 
Gift Certificate

Just updated to the latest bazaar and we're using the Gift Certificates module that TCS wrote (and to which I contributed). I'm not sure if something changed with regard to shipping in particular but it now appears that any orders with Shipping costs are not getting calculated correctly. Here's a sample from my Review Order screen.

1x Fantastic Four: Rise of the Silver Surfer $3.99
1x Reefer Madness Got Reefer? Shirt $1.99

Calculate shipping cost
U.S.P.S. Priority Mail: $5.79

Payment method
Gift Certificates: -$17.56
(Where it got this total I'm not sure - 5.79 + 5.98 is $11.57

Subtotal: $5.98

U.S.P.S. Priority Mail: $5.79

Total: -$5.79
Paying by: Zero Total

It appears to me that the two things are calculated separately - the gift certificates Zeroes out the total and then deducts the shipping again which then results in a negative number.

Version: 
beta6