Support for the Ruby 2.4 series has ended. See here for reference.
# File rubygems/commands/help_command.rb, line 293 def execute arg = options[:args][0] _, help = SUBCOMMANDS.find do |command,| begins? command, arg end if help then if Symbol === help then send help else say help end return end if options[:help] then show_help elsif arg then show_command_help arg else say Gem::Command::HELP end end