`frum install 2.6.0` causes an error

[TaKO8Ki]

frum install 2.6.0 caused the following error.

$ frum install 2.6.0
==> Installing Ruby 2.6.0
error: Can't extract the file: IoError(Custom { kind: Other, error: TarError { desc: "failed to unpack `/Users/tako8ki/.frum/versions/.downloads/.tmpLHCLTt/ruby-2.6.0/libexec/bundle`", io: Custom { kind: Other, error: TarError { desc: "failed to unpack `ruby-2.6.0/libexec/bundle` into `/Users/tako8ki/.frum/versions/.downloads/.tmpLHCLTt/ruby-2.6.0/libexec/bundle`", io: Os { code: 20, kind: Other, message: "Not a directory" } } } } })