diff --git a/sys_conn_helper_freebsd.go b/sys_conn_helper_freebsd.go
index 5e635b18df8..a53ca2eae0d 100644
--- a/sys_conn_helper_freebsd.go
+++ b/sys_conn_helper_freebsd.go
@@ -14,7 +14,7 @@ const (
 	ipv4PKTINFO  = 0x7
 )
 
-const ecnIPv4DataLen = 4
+const ecnIPv4DataLen = 1
 
 const batchSize = 8