ff -c not being applied to staged renamed files

[haensch-mauricio]

{lamb} git st
On branch fb-ASIM-1865-generate-trend-from-profile-bug
Changes to be committed:
  (use "git reset HEAD <file>..." to unstage)

        renamed:    source/python/alfasim_gui/plugins/_tests/test_license_manager.py -> source/python/alfasim_gui/plugins/_tests/test_license_manager2.py


(alfasim_gui-py36) W:\1\Projects\alfasim\alfasim_gui {git}
{lamb} git commit
/w/1/Projects/alfasim
Hook fix-format in progress ....
alfasim_gui/source/python/alfasim_gui/plugins/_tests/test_license_manager2.py: Failed

========================================== failed checks ==========================================
alfasim_gui/source/python/alfasim_gui/plugins/_tests/test_license_manager2.py

fix-format check failed (status=1)! To fix, execute:
  ff -c

The command does not fix the file, but pre-commit hook detects it.

If the renamed file is yet unstaged, it works correctly.