diff --git a/ryu/ofproto/ofproto_v1_2.py b/ryu/ofproto/ofproto_v1_2.py
index 9c9c4f95..e9f789ab 100644
--- a/ryu/ofproto/ofproto_v1_2.py
+++ b/ryu/ofproto/ofproto_v1_2.py
@@ -494,7 +494,7 @@ OFP_PORT_STATS_REQUEST_SIZE = 8
 assert calcsize(OFP_PORT_STATS_REQUEST_PACK_STR) == OFP_PORT_STATS_REQUEST_SIZE
 
 # struct ofp_port_stats
-OFP_PORT_STATS_PACK_STR = '!H6xQQQQQQQQQQQQ'
+OFP_PORT_STATS_PACK_STR = '!I4xQQQQQQQQQQQQ'
 OFP_PORT_STATS_SIZE = 104
 assert calcsize(OFP_PORT_STATS_PACK_STR) == OFP_PORT_STATS_SIZE