CustomNameVisible does not show on WitherSkulls

What I expected to happen was an invisible WitherSkull with a visible name, so there would be floating text.
What actually happened was the chat just said "Unable to summon object."

Steps to Reproduce:
1. Type "/summon WitherSkull ~ ~1 ~

{CustomName:"Text",CustomNameVisible:1,Direction:[0.0,0.0,0.0]}

" into chat or a command block. (It might be "Motion:[0.0,0.0,0.0]")