Passenger can't start application because of Ruby syntax error

I'm trying to run a rails app and am getting this error message:

/Library/Ruby/Gems/2.0.0/gems/attribute_extras-0.1.3/lib/attribute_extras.rb:24: syntax error, unexpected ',' ...er_extra(verb, function, past:, validator:, options: nil)

I'm running ruby 2.1.7.

P.S. (full trace)

/Library/Ruby/Gems/2.0.0/gems/attribute_extras-0.1.3/lib/attribute_extras.rb:50: syntax error, unexpected keyword_end, expecting end-of-input (SyntaxError) /Library/Ruby/Gems/2.0.0/gems/bundler-1.10.6/lib/bundler/runtime.rb:76:in require' /Library/Ruby/Gems/2.0.0/gems/bundler-1.10.6/lib/bundler/runtime.rb:76:inblock (2 levels) in require' /Library/Ruby/Gems/2.0.0/gems/bundler-1.10.6/lib/bundler/runtime.rb:72:in each' /Library/Ruby/Gems/2.0.0/gems/bundler-1.10.6/lib/bundler/runtime.rb:72:inblock in require' /Library/Ruby/Gems/2.0.0/gems/bundler-1.10.6/lib/bundler/runtime.rb:61:in each' /Library/Ruby/Gems/2.0.0/gems/bundler-1.10.6/lib/bundler/runtime.rb:61:inrequire' /Library/Ruby/Gems/2.0.0/gems/bundler-1.10.6/lib/bundler.rb:134:in require' /Users/adamjohnson/Documents/rails/platform/config/application.rb:7:in' /Users/adamjohnson/Documents/rails/platform/config/environment.rb:2:in require' /Users/adamjohnson/Documents/rails/platform/config/environment.rb:2:in' config.ru:3:in require' config.ru:3:inblock in ' /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:55:in instance_eval' /Library/Ruby/Gems/2.0.0/gems/rack-1.6.4/lib/rack/builder.rb:55:ininitialize' config.ru:1:in new' config.ru:1:in' /Library/Ruby/Gems/2.0.0/gems/passenger-5.0.21/src/helper-scripts/rack-preloader.rb:110:in eval' /Library/Ruby/Gems/2.0.0/gems/passenger-5.0.21/src/helper-scripts/rack-preloader.rb:110:inpreload_app' /Library/Ruby/Gems/2.0.0/gems/passenger-5.0.21/src/helper-scripts/rack-preloader.rb:156:in <module:App>' /Library/Ruby/Gems/2.0.0/gems/passenger-5.0.21/src/helper-scripts/rack-preloader.rb:30:in' /Library/Ruby/Gems/2.0.0/gems/passenger-5.0.21/src/helper-scripts/rack-preloader.rb:29:in `'