That's strange, I've just tested it and it works on a new game.You have one full friendship heart, correct? Is it an old save?
Yes, one heart is full, and I'm using the save from the previous version.
Okay, it's a bigger thing than I thought, I'll upload an update when I'll have fixed it.
Thanks for reporting it.
Edit : Done, you can try version 0.2.4b
You're welcome, and thanks for fixing it.