Lux Ultimate Skill (R) bug

When you die while casting your ult with Lux and it doesn't go off, after respawning you can't see a cooldown on it, however for several seconds you can't use it either.

It happens every time I die while casting ult and its frustrating, because many times i lose a potential kill thinking that i have it up when i actually don't.

Edit: Managed to do it in the practice tool. https://youtu.be/WKEMWLhXXq8