diff --git a/protos/openolt.proto b/protos/openolt.proto
index e6bb0b5..ddc8f74 100644
--- a/protos/openolt.proto
+++ b/protos/openolt.proto
@@ -246,7 +246,7 @@
 message OnuPacket {
     fixed32 intf_id = 1;
     fixed32 onu_id = 2;
-    fixed64 port_no = 4;
+    fixed32 port_no = 4;
     bytes pkt = 3;
 }