[GAMEPLAY] Malzahar's passive not blocking damage

Was just playing an ARAM with a Malz on my team. He had his passive up, got hit by a Varus Q, and took full damage from it. I believe Varus had Dirk's passive active when he hit Malzahar, but besides that, I have no idea how to recreate this, or what caused it. Caution: Loud audio due to loud fan: http://plays.tv/video/59a89d7c3a9d859385/what-