Xerath Ultimate bug?

idk if this is apart of xeraths mechanics, or some sort of nerf to him, but i havent played xerath in a while, and i got him today in an aram. I noticed when i got level 6 that when i ulted and actually casted my ult the first shot went underneath me. So i thought maybe i should wait a bit longer before i cast it, the next ult i did so and still went underneath me, after that i went a bit over board and waited about 2 or 3 seconds before i actually casted the ult for the first time and it went where i told it too. so im not sure if it is actually a bug or some sort of nerf or new mechanics to xeraths kit.