diff --git a/lv/lv0500a.uml b/lv/lv0500a.uml
index dce5ab7c7..e9001a985 100755
--- a/lv/lv0500a.uml
+++ b/lv/lv0500a.uml
@@ -193,6 +193,7 @@ BEGIN
   DISPLAY "Descrizione@50" S0
   OUTPUT F_S_FREQ CODTAB
   FLAGS "Z"
+  CHECKTYPE REQUIRED
   FIELD FREQ
 END