Ryze ulti and LB e bug [GAMEPLAY]

When i played ryze yesterday, something happend. I used was going to use ulti, and zhonya's. So - I used ulti, a Le blank used e on me, and i used zhonya's to prevent the snare. but when the LB e went off, my ulti was canceled. this happend twice so i dont think it is hard to reproduce.

So u shall use a ryze ulti (Lv2 ulti) - A Le Blank shall e you, and then use zhonya's. When LB's e procs will our ulti get canceled. I think this happens every time but im now sure.