Killing a mob with oozing effect crashes game.

Game crashed when I killed a baby zombie with oozing effect in Trail Chamber. Starting game again crashes also - game just saves at the moment when the baby zombie is being killed and crashes every time with error: "The game crashed whilst ticking entity. Error: java.lang.ClassFormatError: Method in a class brs$a has illegal modifiers: 0x8". Not sure if this bug occurs with other mobs though.