diff --git a/loopback/locale/es.json b/loopback/locale/es.json
index e2194b8ada..872d45ae09 100644
--- a/loopback/locale/es.json
+++ b/loopback/locale/es.json
@@ -181,5 +181,6 @@
 	"This specie already exist": "Esta especie ya existe",
 	"Client assignment has changed": "He cambiado el comercial ~*\"<{{previousWorkerName}}>\"*~ por *\"<{{currentWorkerName}}>\"* del cliente [{{clientName}} ({{clientId}})]({{{url}}})",
 	"None": "Ninguno",
-	"The contract was not active during the selected date": "El contrato no estaba activo durante la fecha seleccionada"
+	"The contract was not active during the selected date": "El contrato no estaba activo durante la fecha seleccionada",
+	"This document already exists on this ticket": "Este documento ya existe en el ticket"
 }
\ No newline at end of file
diff --git a/modules/ticket/back/models/ticket-dms.js b/modules/ticket/back/models/ticket-dms.js
index ddb338632e..9bceaae6eb 100644
--- a/modules/ticket/back/models/ticket-dms.js
+++ b/modules/ticket/back/models/ticket-dms.js
@@ -1,3 +1,11 @@
+const UserError = require('vn-loopback/util/user-error');
+
 module.exports = Self => {
     require('../methods/ticket-dms/removeFile')(Self);
+
+    Self.rewriteDbError(function(err) {
+        if (err.code === 'ER_DUP_ENTRY')
+            return new UserError('This document already exists on this ticket');
+        return err;
+    });
 };
diff --git a/modules/ticket/back/models/ticket-dms.json b/modules/ticket/back/models/ticket-dms.json
index b7b24dce00..8bcff254c6 100644
--- a/modules/ticket/back/models/ticket-dms.json
+++ b/modules/ticket/back/models/ticket-dms.json
@@ -12,7 +12,7 @@
     },
     "properties": {
         "dmsFk": {
-            "type": "Number",
+            "type": "number",
             "id": true,
             "required": true
         }