diff --git a/src/python/oftest/testutils.py b/src/python/oftest/testutils.py
index 980099f..5c3f6f3 100644
--- a/src/python/oftest/testutils.py
+++ b/src/python/oftest/testutils.py
@@ -673,6 +673,7 @@
 
     msg = ofp.message.packet_out()
     msg.in_port = ing_port
+    msg.buffer_id = 0xffffffff
     msg.data = str(pkt)
     if action_list is not None:
         for act in action_list: