Bukkit

What steps will reproduce the problem?
1. Get a bow
2. Headshot a Creeper (I only tested these, Zombies and Zombie Pigmen)
3. Profit

What is the expected output? What do you see instead?
The creeper should be knockbacked, but it doesn't.

What version of the product are you using?
Bukkit: 1.4.7 R1.0
CombatCrits: v.1.6
Java: 7

Do you have an error log of what happened?
No, the log is perfectly clean.

Please provide any additional information below.
Here's my config:

NutShotDamage: 4
HeadshotDamage: 6
PvPKnockoutDamage: 3
TextAlert: true
CustomMessageToggle: true
CustomMessage: §cBOOM Headshot!
AxeCrusherCooldown: -1
DashCooldown: -1

Thanks!