Unable to convert to F2FS

I just updated my toro to CM 12.1. Everything went smoothly, but when I reboot into recovery (TWRP 2.8.7.0) and go to format either data or cache there's no option for f2fs. There's just a blank spot where that button should be and it gives me all the other file systems I can convert into (ext3, ext4, etc). Any ideas on what's going on and how to fix it? Thanks.