Why does fz insert a back slash prefix when I accept one path in fzf (with z.lua)

[skywind3000]

I am trying to use fz.sh with z.lua by:

function _z() { _zlua "$@"; }
source /path/to/fz.sh
eval "$(lua /path/to/z.lua --init bash enhanced once echo)"

When I input:

z vim<tab>

fzf started as expected:

skywind@weilin0:~$ z vim
> {CURSOR}  12/12
>  /home/skywind/software/vim
   /home/skywind/github/vim
   /mnt/d/acm/github/vim
   /home/skywind/.vim/vim
   /home/skywind/.vim
   /mnt/d/acm/github/vim-init
   /home/skywind/tmp/comma/software/vim
   /mnt/d/ACM/github/vim

but if I accepted the first one, fz inserted a \ before the full path name, and the command line was completed as:

skywind@weilin0:~$ z \ /home/skywind/software/vim/

See the leading strange \.

Any clue for this ??

[skywind3000]

never mind, I figure out myself. z -l outputs one more space in z.lua than z.sh.