Wrong death message of renamed mobs spawned by dispensers

There is a very big bug in the Snapshots. When you spawns a creeper with the name changed (name changed because the anvil) with your hand and he kills you tells what the "Monster green" (name changed) kill you... but when you spawns him with a dispenser and he kills you says: (example) Creeper blows up you. And this happens with all the mobs... Thanks.