Voucher breaks user registration process

I have both the voucher and organic groups regcode modules activated. Once I activate the voucher module, an exception is generated in the user registration process. The error occurs because voucher implements hook_user_presave. The result is that the code tries to assign the user to the organic group before the user account has been saved to the database.

Solution: implementing hook_user_update instead of hook_user_presave fixes the issue for me. I no longer receive an error, and the voucher code is used successfully on update. Patch is attached. Let me know if you have any questions. Thanks!