They were not aligned properly, which causes Black to crash:
```
$ black --version
black, version 20.8b1
$ cat test.py
def f():
# fmt: off
if True:
print()
# fmt: on
def g():
pass
$ black test.py
error: cannot format test.py: INTERNAL ERROR: Black produced code that is not equivalent to the source. Please report a bug on https://github.com/psf/black/issues. This diff might be helpful: /tmp/blk_phpp_27o.log
Oh no! 💥 💔 💥
1 file failed to reformat.
```