diff --git a/boto/swf/layer1.py b/boto/swf/layer1.py
index f11963b8e4..d2b6e4e611 100644
--- a/boto/swf/layer1.py
+++ b/boto/swf/layer1.py
@@ -1152,8 +1152,8 @@ def count_open_workflow_executions(self, domain, latest_date, oldest_date,
         return self.make_request('CountOpenWorkflowExecutions', json_input)
 
     def list_open_workflow_executions(self, domain,
+                                      oldest_date,
                                       latest_date=None,
-                                      oldest_date=None,
                                       tag=None,
                                       workflow_id=None,
                                       workflow_name=None,