diff --git a/frontend/src/locale/index.ts b/frontend/src/locale/index.ts
index dcb1b0bb91..229d2b4552 100644
--- a/frontend/src/locale/index.ts
+++ b/frontend/src/locale/index.ts
@@ -663,7 +663,7 @@ Click the box to change. If left empty, we will assume you are available.`,
     "orderInformation.invalidFiscalCode": "Fiscal code not valid",
     "orderInformation.pec": "PEC",
     "orderInformation.sdi": "SDI",
-    "orderInformation.invalidSDI": "SDI must be 7 characters long",
+    "orderInformation.invalidSDI": "SDI must be 7 characters long (6 for Italian PA)",
 
     "orderQuestions.heading": "Order questions",
     "orderQuestions.attendeeGivenName": "Attendee Given name",
@@ -1447,7 +1447,7 @@ The sooner you buy your ticket, the more you save!`,
     "orderInformation.invalidFiscalCode": "Codice fiscale non valido",
     "orderInformation.pec": "PEC",
     "orderInformation.sdi": "SDI",
-    "orderInformation.invalidSDI": "Il codice SDI deve essere di 7 caratteri",
+    "orderInformation.invalidSDI": "Il codice SDI deve essere di 7 caratteri (6 per una PA)",
 
     "orderQuestions.heading": "Domande aggiuntive",
     "orderQuestions.attendeeName": "Nome partecipante",