Game Mechanics: Double Invisibility

[Treats]

As it is now you are able to have both Regular Invisibility and Invisibility Versus Undead on you at the same time.

This shouldn't be possible.

Casting Invisibility on someone that has Invisibility Versus Undead active should render(and vice versa):

"Soandso tries to cast invisibility on you, but soandso is already invisible"

Something like that, I don't have the exact message.