After a little Googling, I came across this issue posted on the Sidekiq Github account. The recommendation was to add the Sinatra gem, which worked for Sidekiq users. I gave it a try, and that fixed the error for me as well:! Unable to load application: LoadError: cannot load such file -- rack/showexceptions
gem 'sinatra', github: 'sinatra'Just thought I'd throw this up in case anyone else came across this issue.