Preset cannot be found

[tzohpilotl]

I was willing to write a preset but i can't get promptline to load it:
~/.vim/bundle/promptline.vim/autoload/promptline/presets/custom.vim

let g:promptline_preset = {
\'a' : [ promptline#slices#user() ],
\'b' : [ promptline#slices#cwd() ],
\'c' : [ promptline#slices#jobs() ],
\'y' : [ promptline#slices#vcs_branch() ],
\'z' : [ promptline#slices#git_status() ],
\'warn' : [ promptline#slices#last_exit_code() ]}

vim keeps telling me Promptline: preset cannot be found 'custom'. I'm using zsh + xterm.