Accent and gender issues for Full Text Search postgresql

Question

I got two different inputs that should be stemmed to the same output :

SELECT to_tsvector('french', 'fermier'),
       to_tsvector('french', 'fermièr'),
       to_tsvector('french', 'fermiér'),
       to_tsvector('french', 'fermiere'),
       to_tsvector('french', 'fermière'),
       to_tsvector('french', 'fermiére')

-- Output
'fermi':1 'fermier':1 'fermier':1 'fermier':1 'fermi':1 'fermier':1 

Ignoring accent would be possible but it would still collapse output to two differents options : fermier or fermi.
For information, the only difference between fermier and fermiere is the gender, the former is masculine and the latter is feminine.
Thus, issue is that the feminine form is stemmed to the masculine form which is itself stemmed to fermi. I don't understand why stemming is not invariable from gender here.