ruby/rubygems · error · Gem::InstallError

gem #{@gem.inspect} is not installed

Error message

gem #{@gem.inspect} is not installed

What it means

Error "gem #{@gem.inspect} is not installed" thrown in ruby/rubygems.

Source

Thrown at lib/rubygems/uninstaller.rb:107

  end

  ##
  # Performs the uninstall of the gem.  This removes the spec, the Gem
  # directory, and the cached .gem file.

  def uninstall
    dependency = Gem::Dependency.new @gem, @version

    list = []

    specification_record.stubs.each do |spec|
      next unless dependency.matches_spec? spec

      list << spec
    end

    if list.empty?
      raise Gem::InstallError, "gem #{@gem.inspect} is not installed"
    end

    default_specs, list = list.partition(&:default_gem?)
    warn_cannot_uninstall_default_gems(default_specs - list)
    @default_specs_matching_uninstall_params = default_specs.map(&:to_spec)

    list, other_repo_specs = list.partition do |spec|
      @gem_home == spec.base_dir ||
        (@user_install && spec.base_dir == @user_dir)
    end

    list.sort!

    if list.empty?
      return unless other_repo_specs.any?

      other_repos = other_repo_specs.map(&:base_dir).uniq

View on GitHub (pinned to 86cbb817a3)

Solutions

1. Check the gem name with `gem list` and uninstall the installed name
2. Specify the exact version with `-v` if multiple versions exist

When it happens

Trigger: Thrown at lib/rubygems/uninstaller.rb:107 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of ruby/rubygems@86cbb817a3 (2026-08-23). Data as JSON: /api/errors/5e44f32f89b53e76. Report an issue: GitHub.