diff --git a/mg/batbgsa.uml b/mg/batbgsa.uml
index cfb78101d..32a17eb64 100755
--- a/mg/batbgsa.uml
+++ b/mg/batbgsa.uml
@@ -355,7 +355,7 @@ BEGIN
   FLAGS "L"
   GROUP 3
   DRIVENBY F_FORMAT
-  STR_EXPR LEN(#F_FORMAT)<=20
+  STR_EXPR STR(LEN(#F_FORMAT)<=20)
   WARNING "Il formato dell'articolo non puo' superare i 20 caratteri"
 END