Mobs with fire resistance still appear to catch fire when swimming in lava

Expected behavior: mobs with fire resistance should never appear to be on fire.

Observed behavior: mobs with fire resistance look like they are on fire when they are in contact with lava.

To reproduce: either find a mob with natural fire resistance (zombie pigmen, the player in creative, etc) or throw a splash potion of fire resistance at any old mob, and push it into lava.

This is particularly jarring with ghasts, which transform into giant fireballs whenever they fly into one of the many lavafalls in the Nether, and extremely distracting for the player in creative mode because the first person view will be obstructed by fire.