diff --git a/common/lib/xmodule/xmodule/combined_open_ended_module.py b/common/lib/xmodule/xmodule/combined_open_ended_module.py
index 3e0a3b27a5..7ff9df2c24 100644
--- a/common/lib/xmodule/xmodule/combined_open_ended_module.py
+++ b/common/lib/xmodule/xmodule/combined_open_ended_module.py
@@ -29,6 +29,7 @@ VERSION_TUPLES = (
 )
 
 DEFAULT_VERSION = 1
+DEFAULT_VERSION = str(DEFAULT_VERSION)
 
 class CombinedOpenEndedModule(XModule):
     """