Strange bash errors for root console

Frequently, when switching my user by root with su -, I get strange bash error messages in the rxvt console, or even in a TTY. They happen even after a complety system upgrade from scratch, so it is probably a thing in root HOME. For example, these: sh: error importing function definition for `_file' sh: _file: line 3: syntax error near unexpected token `(' sh: _file: line 3: ` --help | --version | --separator | -!(-*)[vF])' When I logout, I then get several errors like: /bin/bash: _sudo: line 19: syntax error near unexpected token `(' /bin/bash: _sudo: line 19: ` --user | --other-user | -!(-*)[uU])' /bin/bash: error importing function definition for `_sudo' Even if I do sh in the console I get /bin/bash: _file: line 3: syntax error near unexpected token `(' /bin/bash: _file: line 3: ` --help | --version | --separator | -!(-*)[vF])' /bin/bash: error importing function definition for `_file' I then logout and login again, and the normal behavior is restored. Until it begins behaving strangely... I thought it was a problem with '~/.bashrc' or the like, but those files are shared with my normal user that never ever shows errors in console. There is obviously a bash script with errors, but I don't know even where to begin looking. What is _sudo?? The commands grep _sudo $(find . -type f) and find . -name _sudo show nothing... **EDIT** This is the content of my file /usr/share/bash-completion/completions/sudo: # bash completion for sudo(8) -*- shell-script -*- _sudo() { local cur prev words cword split _init_completion -s || return local i mode=normal [[ $1 == *sudoedit ]] && mode=edit [[ $mode == normal ]] && for ((i = 1; i <= cword; i++)); do if [[ ${words[i]} != -* ]]; then local PATH=$PATH:/sbin:/usr/sbin:/usr/local/sbin local root_command=${words[i]} _command_offset $i return fi if [[ ${words[i]} == -@(!(-*)e*|-edit) ]]; then mode=edit break fi [[ ${words[i]} == \ -@(user|other-user|group|close-from|prompt|!(-*)[uUgCp]) ]] && ((i++)) done case "$prev" in --user | --other-user | -!(-*)[uU]) COMPREPLY=($(compgen -u -- "$cur")) return ;; --group | -!(-*)g) COMPREPLY=($(compgen -g -- "$cur")) return ;; --close-from | --prompt | -!(-*)[Cp]) return ;; esac $split && return if [[ $cur == -* ]]; then local opts=$(_parse_help "$1") COMPREPLY=($(compgen -W '${opts:-$(_parse_usage "$1")}' -- "$cur")) [[ ${COMPREPLY-} == *= ]] && compopt -o nospace return fi if [[ $mode == edit ]]; then _filedir fi } && complete -F _sudo sudo sudoedit # ex: filetype=sh