diff --git a/lib/capybara/selenium/driver.rb b/lib/capybara/selenium/driver.rb
index 018f59eb..3caabfa9 100644
--- a/lib/capybara/selenium/driver.rb
+++ b/lib/capybara/selenium/driver.rb
@@ -28,6 +28,7 @@ class Capybara::Selenium::Driver < Capybara::Driver::Base
   def initialize(app, options={})
     @app = app
     @browser = nil
+    @exit_status = nil
     @options = DEFAULT_OPTIONS.merge(options)
     @rack_server = Capybara::Server.new(@app)
     @rack_server.boot if Capybara.run_server