diff --git a/oltbase.py b/oltbase.py
index be7f0af..fff3740 100644
--- a/oltbase.py
+++ b/oltbase.py
@@ -73,7 +73,7 @@
         self.controller.message_send(request)
         do_barrier(self.controller)
 
-    def testPacketFlow(self, c_vlan_id, s_vlan_id, onu = None):
+    def testPacketFlow(self, s_vlan_id, c_vlan_id, onu = None):
 
         incorrectTagPkt = simple_udp_packet(pktlen=100, dl_vlan_enable=True, vlan_vid=100, vlan_pcp=1)
         zeroTaggedPkt = simple_udp_packet(pktlen=100, dl_vlan_enable=True, vlan_vid=0, vlan_pcp=0)