diff --git a/moto/dynamodb2/responses.py b/moto/dynamodb2/responses.py
index acc9dfb5e..d41e4b366 100644
--- a/moto/dynamodb2/responses.py
+++ b/moto/dynamodb2/responses.py
@@ -148,10 +148,13 @@ class DynamoHandler(BaseResponse):
         res = re.search('\"\"', json.dumps(item))
         if res:
             er = 'com.amazonaws.dynamodb.v20111205#ValidationException'
-            return 400, {'server': 'amazon.com'}, dynamo_json_dump(
-                {'__type': er,
-                'message': ('One or more parameter values were invalid: '
-                'An AttributeValue may not contain an empty string')})
+            return (400,
+                {'server': 'amazon.com'},
+                dynamo_json_dump({'__type': er,
+                                'message': ('One or more parameter values were '
+                                            'invalid:An AttributeValue may not '
+                                            'contain an empty string')}
+                                 ))
 
         overwrite = 'Expected' not in self.body
         if not overwrite: