curse of gwalhur against magic?

Hi, I'm not trying to spread rumours but I was told that despite what the description of curse of gwalhur feat says the magic attackers receive unholy damage too. Has anybody test it?

I'd do myself but I'm broke and I don't want to spend 1Gold to test something I'm almost sure is not true.

Works, i remember breaking Shield of the risen with it & Lsparks.

It works against anything that attacks you >.<