Tellraw is broken again.

Tellraw just doesn't work. No matter what I do, it says "Invalid json: malformed JSON at line 1 column 3. I am aware that this was an issue in a previous snapshot that was supposedly fixed. Well, it's back now. Either that, or the usage of Tellraw has changed, but I haven't seen anything about that in the patch notes. Can people verify that this is in fact correct usage below?

/tellraw @a

{text:'Yo'}