Enderdragon does not have a radii option

The Ender Dragon is no being affected by the radius selector in commands.
For instance this command does not work
tp @e[type=EnderDragon,r=20] ~ ~ ~-0.1

however it still works fine on other entities such as cow etc.

UPDATE: This is still a problem in 1.9 pre-v4 even though it say fixed on the change log.