When upgrading to hyper-spec i get a strange uninitialized constant Selenium::WebDriver::Firefox::Service although i don't user Selenium::WebDriver::Firefox::Service anywhere in my code (only references to Selenium::WebDriver::Firefox) A solution i have found and according to https://github.com/titusfortner/webdrivers Is to try and execute: Webdrivers::Geckodriver.update in rails console. This updates the local Geckodriver automatically as @catmando noted, if hyper-spec is both in test and development environment 'rails c' might be unusable so remove it temporarilly from the dev env