diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
index 7689e7bee..205d7ea96 100644
--- a/spec/spec_helper.rb
+++ b/spec/spec_helper.rb
@@ -23,6 +23,7 @@
 $LOAD_PATH.unshift(File.join(File.dirname(__FILE__), "..", "lib"))
 
 require "ostruct"
+require "stringio"
 require "bson"
 require "json"
 require "rspec"