Word under cursor appears in completion

[astier]

Minimal vimrc

call plug#begin($XDG_DATA_HOME.'/nvim/plugins')
    Plug 'nvim-lua/completion-nvim'
    Plug 'steelsojka/completion-buffers'
cal plug#end()
autocmd bufenter * lua require'completion'.on_attach()
let g:completion_chain_complete_list = [{'complete_items': ['buffer']}]
set completeopt=menuone,noinsert

Steps to reproduce

1. Open minimal vimrc
2. Enter new line with o
3. Type cal
4. Notice how the completion shows cal and call

Expected behavior

The completions should not show cal but only call because cal is already typed.