diff --git a/src/redturtle/prenotazioni/adapters/booker.py b/src/redturtle/prenotazioni/adapters/booker.py
index 9794a78d..3f512408 100644
--- a/src/redturtle/prenotazioni/adapters/booker.py
+++ b/src/redturtle/prenotazioni/adapters/booker.py
@@ -1,5 +1,4 @@
 # -*- coding: utf-8 -*-
-import json
 import math
 from datetime import timedelta
 from random import choice
@@ -192,10 +191,7 @@ def generate_params(self, data, force_gate, duration):
         if fiscalcode:
             params["fiscalcode"] = fiscalcode.upper()
 
-        additional_fields = data.get("additional_fields", "")
-
-        if additional_fields:
-            params["additional_fields"] = json.dumps(additional_fields)
+        params["additional_fields"] = data.get("additional_fields", [])
 
         return params
 
diff --git a/src/redturtle/prenotazioni/content/prenotazione.py b/src/redturtle/prenotazioni/content/prenotazione.py
index f21392c2..946e05ff 100644
--- a/src/redturtle/prenotazioni/content/prenotazione.py
+++ b/src/redturtle/prenotazioni/content/prenotazione.py
@@ -4,6 +4,7 @@
 import six
 from DateTime import DateTime
 from plone import api
+from plone import schema as plone_schema
 from plone.app.event.base import default_timezone
 from plone.app.z3cform.widget import DatetimeFieldWidget
 from plone.autoform import directives
@@ -188,9 +189,11 @@ class IPrenotazione(model.Schema):
 
     # Schema is defined in PrenotaizioneType ad an datagridfield, and here we save the data as an json
     # in base of selected type
-    additional_fields = schema.TextLine(
+    additional_fields = schema.List(
         title="Additional fields, not editable",
         required=False,
+        value_type=plone_schema.JSONField(),
+        default=[],
     )
 
     directives.widget(
diff --git a/src/redturtle/prenotazioni/restapi/serializers/adapters/prenotazione.py b/src/redturtle/prenotazioni/restapi/serializers/adapters/prenotazione.py
index 4c4bd2e3..227199b9 100644
--- a/src/redturtle/prenotazioni/restapi/serializers/adapters/prenotazione.py
+++ b/src/redturtle/prenotazioni/restapi/serializers/adapters/prenotazione.py
@@ -100,9 +100,7 @@ def __call__(self, *args, **kwargs):
             "requirements": requirements,
             "modification_date": json_compatible(self.prenotazione.modified()),
             "creation_date": json_compatible(self.prenotazione.created()),
-            "additional_fields": json.loads(
-                self.prenotazione.additional_fields or "[]"
-            ),
+            "additional_fields": self.prenotazione.additional_fields,
         }
 
 
@@ -137,9 +135,7 @@ def __call__(self, *args, **kwargs):
             "email": self.prenotazione.email,
             "fiscalcode": self.prenotazione.fiscalcode,
             "phone": self.prenotazione.phone,
-            "additional_fields": json.loads(
-                self.prenotazione.additional_fields or "[]"
-            ),
+            "additional_fields": self.prenotazione.additional_fields,
             "staff_notes": self.prenotazione.staff_notes,
             "company": self.prenotazione.company,
             "vacation": self.prenotazione.isVacation(),
diff --git a/src/redturtle/prenotazioni/restapi/services/booking/update.py b/src/redturtle/prenotazioni/restapi/services/booking/update.py
index 3987ee99..7204df5a 100644
--- a/src/redturtle/prenotazioni/restapi/services/booking/update.py
+++ b/src/redturtle/prenotazioni/restapi/services/booking/update.py
@@ -2,6 +2,7 @@
 import json
 
 from plone import api
+from plone.restapi.deserializer import json_body
 from plone.restapi.services.content.update import ContentPatch
 from zExceptions import BadRequest
 from zope.component import getUtility
@@ -19,7 +20,7 @@ def reply(self, *args, **kwargs):
         return super().reply(*args, **kwargs)
 
     def handle_additional_fields(self):
-        data = json.loads(self.request.get("BODY", b"").decode())
+        data = json_body(self.request)
         booking_folder = self.context.getPrenotazioniFolder()
 
         if data:
@@ -97,6 +98,4 @@ def handle_additional_fields(self):
                         {"name": field.get("name"), "value": field.get("value")}
                     )
 
-                data["additional_fields"] = json.dumps(additional_fields_data)
-
             self.request["BODY"] = json.dumps(data).encode()