ruby/rubygems · error · ArgumentError

duplicate source #{source_description} for gem #{name}

Error message

duplicate source #{source_description} for gem #{name}

What it means

Error "duplicate source #{source_description} for gem #{name}" thrown in ruby/rubygems.

Source

Thrown at lib/rubygems/request_set/gem_dependency_api.rb:705

  ensure
    @current_groups = nil
  end

  ##
  # Pins the gem +name+ to the given +source+.  Adding a gem with the same
  # name from a different +source+ will raise an exception.

  def pin_gem_source(name, type = :default, source = nil)
    source_description =
      case type
      when :default then "(default)"
      when :path    then "path: #{source}"
      when :git     then "git: #{source}"
      when :source  then "source: #{source}"
      else               "(unknown)"
      end

    raise ArgumentError,
      "duplicate source #{source_description} for gem #{name}" if
        @gem_sources.fetch(name, source) != source

    @gem_sources[name] = source
  end

  private :pin_gem_source

  ##
  # :category: Gem Dependencies DSL
  #
  # Block form for restricting gems to a set of platforms.
  #
  # The gem dependencies platform is different from Gem::Platform.  A platform
  # gem.deps.rb platform matches on the ruby engine, the ruby version and
  # whether or not windows is allowed.
  #
  # :ruby, :ruby_XY ::

View on GitHub (pinned to 86cbb817a3)

Solutions

1. Remove the duplicate source block/option for the named gem in the Gemfile/gem.deps.rb

When it happens

Trigger: Thrown at lib/rubygems/request_set/gem_dependency_api.rb:705 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/afe2df80678b3b9c. Report an issue: GitHub.