I killed the ender dragon and last hit it by exploding a bed under it. It died and gave XP as it should, but I didn't get the "Free the End" advancement.

Steps to Reproduce:
1. Get the ender dragon's health low however you want (bow, beds, etc).
2. Last hit it by exploding a bed underneath it.

3. The advancement isn't given (but you can get the one for holding the dragon egg).