diff --git a/example/Gemfile b/example/Gemfile
index dd6c6d4d..7596b39b 100644
--- a/example/Gemfile
+++ b/example/Gemfile
@@ -1,5 +1,7 @@
 source 'https://rubygems.org'
 
+ruby '2.3.3'
+
 gem 'rails', '4.2.5.1'
 gem 'sqlite3'
 gem 'spring', group: :development