Karthus Visual Bug

I was playing PentaKill Karthus, so I am unsure if this is just a visual bug with that specific skin, or with Karthus in general. When you acquire a Buff, it appears visually twice. After Karthus dies, the buff will continue to spin around Karthus, however none of the effects are in place. Everyone else can see that I have an apparent 'buff', even though I do not.