If I cast Heroism on a character frightened, does it break the effect?

@YYZhedIf I cast Heroism on a party member who is currently frightened, does it break the effect? I say so, DM unsure. as written, breaks the effect, though DM has final say

— Mike Mearls (@mikemearls) February 4, 2016

The heroism spell would suppress a frightening effect that was already on its target. #DnD https://t.co/bGJ1WtS3Tl

— Jeremy Crawford (@JeremyECrawford) February 8, 2016