diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 2130dc20ced..97384e0278b 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -1,5 +1,6 @@
 require 'csl'
 require 'json'
+require 'yaml'
 
 STYLE_ROOT = File.expand_path('../..', __FILE__)