Darius and Snares [GAMEPLAY]

I don't know if this is in fact a bug, or if it is intentional, but, I'm reporting it anyway, just to be safe.

When playing Darius, if snared, his ultimate becomes uncastable, and is interrupted mid-cast if snared. Should this be the case, considering his ult is not a movement-related spell?

Reproduction Steps: Play Darius Get snared within Ultimate Range (I was snared by Morgana, if that changes anything) Try to ult.

Happened in one game so far, will test some more with him to make sure it wasn't a one-off bug. Can't get video evidence, due to no recording.