Night-killer talent bug

Hey
I think I have found a bug to the Night-killer talent (casted by bahamut)

I challenged someone in ladder !
My bahamut got on first cause it was faster!
His came second and it had nightfall talent so it casted Nightfall!

My bahamut has Nightkiller talent ... But it did get activated ignoring the fact that the weather Nightfall! I tried it tree more times and it didn't work again!

Thanks in advance
11121314

Ps. I am going to search for more things that can help!