portsから入れたzshで補完機能を有効にしつつ、mount [TAB]やるとエラーが出る

さっき気がついた。

_mount:575: failed to load module: zsh/regex
_mount:575: -regex-match not available for regex

補完ってどこで定義してるんだっけ？
探索の旅開始。

追記
発見。

/usr/local/share/zsh/4.3.6/functions/Completion/Unix/_mount

追記2
575行付近。

    if [[ "${OSTYPE}" =~ freebsd.* ]]; then
      _fs_msdosfs=( "$_fs_msdos[@]" )
    fi

追記3

  freebsd*|dragonfly*)
    _fs_any=(
      '(sync)async[do all I/O asynchronously]'
      'current[use current options on already mounted file system]'
      'force[force R/W mount of unclean filesystem]'
      'fstab[use options listed in /etc/fstab]'
      'noasync[do I/O synchronously]'
      "noatime[don't update access time]"
      'noauto[can only be mounted explicitly]'
      'noclusterr[disable read clustering]'
      'noclusterw[disable write clustering]'
      "nodev[don't interpret devices]"
      "noexec[don't allow execution of binaries]"
      'nosuid[ignore suid and sgid bits]'
      "nosymfollow[don't follow symlinks]"
      'rdonly[mount file system read-only]'
      '(async)sync[do all I/O synchronously]'
      'suiddir[allow suid bits on directories]'
      'update[change status of already mounted filesystem]'
      'union[cause the namespace at the mount point to appear as the union of the mounted filesystem and the existing directory]'
    )
    _fs_cd9660=(
      'extatt[enable the use of extended attributes]'
      'gens[do not strip version numbers on files]'
      'nojoliet[do not use any Joliet extensions]'
      'norrip[do not use any Rockridge extensions]'
      'nostrictjoliet[relax checking for Supplementary Volume Descriptor Flags field]'
    )
    _fs_std=(
      "nodev[don't interpret devices]"
      "noexec[don't allow execution of binaries]"
      'nosuid[ignore suid and sgid bits]'
      'rdonly[mount file system read-only]'
      'union[cause the namespace at the mount point to appear as the union of the mounted filesystem and the existing directory]'
    )
    _fs_devfs=( "$_fs_std[@]" )
    _fs_fdesc=( "$_fs_std[@]" )
    _fs_kernfs=( "$_fs_std[@]" )
    _fs_linprocfs=( "$_fs_std[@]" )
    _fs_procfs=( "$_fs_std[@]" )
    _fs_msdos=(
      'shortnames[force only the old MS-DOS 8.3 style filenames to be visible]'
      'longnames[force Windows 95 long filenames to be visible]'
      'nowin95[completely ignore Windows 95 extended file information]'
    )
    if [[ "${OSTYPE}" =~ freebsd.* ]]; then
      _fs_msdosfs=( "$_fs_msdos[@]" )
    fi
    ;;

追記4
portsのオプション。NO_SHAREDかWITH_ZSH_PCREが悪さしてるのかな？

NO_SHARED=yes ZSH_ETCDIR=/usr/local/etc/zsh WITH_ZSH_PCRE=yes