diff --git a/ryu/app/simple_switch.py b/ryu/app/simple_switch.py
old mode 100644
new mode 100755
index 16f26b99c..25227f216
--- a/ryu/app/simple_switch.py
+++ b/ryu/app/simple_switch.py
@@ -84,7 +84,7 @@ def _packet_in_handler(self, ev):
     def _port_status_handler(self, ev):
         msg = ev.msg
         reason = msg.reason
-        port_no = msg.port_no
+        port_no = msg.desc.port_no
 
         ofproto = msg.datapath.ofproto
         if reason == ofproto.OFPPR_ADD: