diff --git a/ryu/ofproto/ofproto_v1_2_parser.py b/ryu/ofproto/ofproto_v1_2_parser.py
index <HASH>..<HASH> 100644
--- a/ryu/ofproto/ofproto_v1_2_parser.py
+++ b/ryu/ofproto/ofproto_v1_2_parser.py
@@ -584,7 +584,7 @@ class OFPAction(OFPActionHeader):
 @OFPAction.register_action_type(ofproto_v1_2.OFPAT_OUTPUT,
                                 ofproto_v1_2.OFP_ACTION_OUTPUT_SIZE)
 class OFPActionOutput(OFPAction):
-    def __init__(self, port, max_len):
+    def __init__(self, port, max_len=0):
         super(OFPActionOutput, self).__init__()
         self.port = port
         self.max_len = max_len
of<I>: set ActionOutput default max_len to zero

same as of<I>.