diff --git a/cmd/goyacc/yacc.go b/cmd/goyacc/yacc.go
index d831f673..5e77e2f5 100644
--- a/cmd/goyacc/yacc.go
+++ b/cmd/goyacc/yacc.go
@@ -387,6 +387,8 @@ func setup() {
 	yaccpar = strings.Replace(yaccpartext, "$$", prefix, -1)
 	openup()
 
+	fmt.Fprintf(ftable, "// Code generated by goyacc. DO NOT EDIT.")
+
 	defin(0, "$end")
 	extval = PRIVATE // tokens start in unicode 'private use'
 	defin(0, "error")