Incorrect interaction between Prevent Damage and Shield Counters

Machine
Machine Posts: 963 Critical Contributor

I have a Swans of Bryn Argoll in play (4/3 creature with Flying, Prevent Damage, and Defender). I gave it Shield 2 by paying the gift cost of Perch Protection. Whenever the Swans block an opposing creature, it loses one of its shield counters. This should NOT happen, as the Swans have prevent damage.