Mode line not working even if everything seems correct

Question

I'm editing a file with the following pattern:

# stock comment
# stock comment
# stock comment
# stock comment
# stock comment

conf
conf

conf
conf

very_long_conf_line_xxxxxx (600+ chars)

It's the stock layout and the file name ends with .conf, so Vim picked it up with ft=conf. It's actually some Nginx configuration, so I inserted a modeline like this:

# stock comment
# stock comment
# stock comment
# stock comment
# stock comment
# vim: set filetype=nginx:

conf
conf

conf
conf

very_long_conf_line (600+ chars)

However, when opening the file again, it's still taken as ft=conf.

:verbose se ml? shows modeline and last set from ~/.vimrc line xx, and :verbose se ft? shows filetype=conf and last set from /usr/share/vim/vim81/filetype.vim.

Why isn't my mode line working? How do I get it to work?

I'm running Vim 8.1 from Ubuntu Eoan.

Answer 1

Vim only checks for "a number of lines at the beginning of the end of the file". By default, only the first and last 5 lines are checked.

From :help 'modeline':

If 'modeline' is on 'modelines' gives the number of lines that is checked for set commands

And from help: 'modelines':

'modelines' 'mls' number (default 5)

If you wish, you can

• :set modelines to a larger number, or
• place the modeline(s) at the beginning or end of the file.