ruby-fikemakerでNameError

filemakerをrequireすると、NameErrorが発生。

irb(main):001:0> require 'filemaker'
Traceback (most recent call last):
       11: from /Users/foo/.rbenv/versions/2.5.3/bin/irb:11:in `<main>'
       10: from (irb):1
        9: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:39:in `require'
        8: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:135:in `rescue in require'
        7: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:135:in `require'
        6: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/filemaker-1.0.0/lib/filemaker.rb:3:in `<top (required)>'
        5: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:70:in `require'
        4: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/2.5.0/rubygems/core_ext/kernel_require.rb:70:in `require'
        3: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/filemaker-1.0.0/lib/filemaker/server.rb:4:in `<top (required)>'
        2: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/filemaker-1.0.0/lib/filemaker/server.rb:5:in `<module:Filemaker>'
        1: from /Users/foo/.rbenv/versions/2.5.3/lib/ruby/gems/2.5.0/gems/filemaker-1.0.0/lib/filemaker/server.rb:6:in `<class:Server>'
NameError (uninitialized constant Filemaker::Server::Forwardable)

先にforwardableをrequireしておけばOK

irb(main):002:0> require 'forwardable'
=> true
irb(main):003:0> require 'filemaker'
=> true
irb(main):004:0>