Is this line new??

[Kazumetsa Raijin]

Vicious Stomp (Combat)
You take advantage of the moment to brutally kick an enemy when he is down.
Prerequisites: Combat Reflexes, Improved Unarmed Strike.
Benefit: Whenever an opponent falls prone adjacent to you, that opponent provokes an attack of opportunity from you. This attack must be an unarmed strike.

Whoa whoa. Has the bolded part always been like this? I don't remember seeing that part from all the times I've looked at it.

[ShadowcatX]

Yes, it has always been like that.

Editted for clarification.

[Imbicatus]

AFAIK, it's always been there. It's not listed in the errata for UC, and it's heavily implied by the feat name and flavor text that it's a kick doing the damage.

[Kazumetsa Raijin]

Damn. I am so blind sometimes!! haha.

That makes the most sense Imbicatus... now why can't they do that for Punishing Kick?!