Hi Karadoc, I´ve seen that you´ve find a way to avoid the python callback to get the cost for upgrading units. Since I would like to add a wonder, which gives a discount on upgrading units and it uses python (in CvGameUtils.py), I believe I have to reactivate the callback. I´ve already found the code I have to change back but before I do it, I have the following questions: 1. Is something elste in K-Mod depending on the new structure of upgrading units? 2. Where there any bugs so you decided to change the original code or was it just for performance? 3. In your opinion, is reactivating a big deal for the performance or will it slow the game just a little bit? Thank you for your answers.