Fortune doesn't work on poisonous potatoes

Fortune doesn't work on poisonous potatoes.

I harvested 100000 potato crops with fortune and 100000 without fortune.

I used scoreboard to count how many crops i mined and carpet mod to count how many potatoes and poisonous potatoes I got.

With fortune: 371677 potatoes and 2049 poisonous potatoes

Without fortune: 539523 potatoes and 1959 poisonous potatoes

Fortune works on potatoes but it doesn't work on poisonous potatoes.