diff --git a/tcp.prs b/tcp.prs
index 02714a0..9239133 100644
--- a/tcp.prs
+++ b/tcp.prs
@@ -21,5 +21,5 @@ Socket =
 
 CreditAmount = @count int / @unbounded =unbounded .
 
-Mode = =bytes / @lines LineMode .
+Mode = =bytes / @lines LineMode / <packet @size int>.
 LineMode = =lf / =crlf .