Aec'letec death gaze confusion

I'm currently doing a no reload run, and beat the bg1 portion tonight, I had some celebratory wine! But during the fight with Aec'letec my main character got the dying effect even though he had a protection from magic scroll on. I was able to win the fight and not lose the run because of arrows of dispelling, but shouldn't my character of been immune to that effect? I've played this game countless times, and every playthrough I solo that fight with some warrior with protection from magic scroll, and they're always immune to death gaze. So what could've possibly changed this playthrough? Honestly my heart was pounding when I saw the "dying" effect on my main character but thankfully the arrows of dispelling worked immediately.