circle.yml in toxiproxy-1.0.0 vs circle.yml in toxiproxy-1.0.2

@@ -3,5 +3,9 @@
     - bundle install
     - ./bin/start-toxiproxy.sh
 test:
   override:
     - bundle exec rake test
+
+machine:
+  ruby:
+    version: 2.4.0