diff --git a/lib/ansible/runner.py b/lib/ansible/runner.py
index 8bdb9b1352e..60fa4b8959a 100755
--- a/lib/ansible/runner.py
+++ b/lib/ansible/runner.py
@@ -62,6 +62,8 @@ def _executor_hook(job_queue, result_queue):
 
 class Runner(object):
 
+    _external_variable_script = None
+
     def __init__(self, 
         host_list=C.DEFAULT_HOST_LIST, 
         module_path=C.DEFAULT_MODULE_PATH,