diff --git a/common/lib/xmodule/capa_module.py b/common/lib/xmodule/capa_module.py
index 6b03647cd9..048297e376 100644
--- a/common/lib/xmodule/capa_module.py
+++ b/common/lib/xmodule/capa_module.py
@@ -5,6 +5,7 @@ import json
 import logging
 import traceback
 import re
+import StringIO
 
 from datetime import timedelta
 from lxml import etree