"Narrator" (CTRL+B) doesn't work for me in the newest snapshot 17w13a

Narrator
CTRL + B to activate
Reads chat text aloud

Just downloaded the newest snapshot and just wanted to play around with this narrator thing, but the problem is that the CTRL + B just won't work. I've turned all my sounds up to 100% and nothing. I tried to relog, restart pc and stuff. Is there an option somewhere that poor I can't find? Am I doing something wrong? I think its a bug.