Vim Nerdcommenter custom delimiters does not work -

i attempting follow advice here:

and here:

when declare own customdelimiters in .vimrc file, nerdcommenter not appear recognize them.

i have put lines

let g:nerdcustomdelimiters = {     \ 'blahblah': { 'left': '#'} \ }

into .vimrc, whenever open file called a.blahblah, still default /*...*/ commenting behavior. if attempt use <leader>ca, told

"nerdcommenter:cannot use alternative delimiters, none specified"

i have moved above lines head , tail of .vimrc file, same behavior.

thank help.

when set g:nerdcustomdelimiters, ask nerd-commenter plugin change delimiters specific file types.

unless added this, blahblah not known file type, when edit a.blahblah, no file type defined, , nerd-commenter delimiters default ones.

after opening file, can manually change current file type doing:

set ft=blahblah

then example should work.

Live one