diff --git a/src/pretix/base/datasync/datasync.py b/src/pretix/base/datasync/datasync.py
index 921e8d14d5..d5bfd304c4 100644
--- a/src/pretix/base/datasync/datasync.py
+++ b/src/pretix/base/datasync/datasync.py
@@ -25,7 +25,7 @@ import logging
 from collections import namedtuple
 from datetime import timedelta
 from functools import cached_property
-from typing import Optional, Protocol
+from typing import List, Optional, Protocol
 
 import sentry_sdk
 from django.db import DatabaseError, transaction
@@ -176,7 +176,7 @@ class OutboundSyncProvider:
                 - `pretix_id_field`: Which pretix data field should be used to identify the mapped object. Any ``DataFieldInfo.key``
                   returned by ``sourcefields.get_data_fields()`` for the combination of ``Event`` and ``pretix_model``.
                 - `external_id_field`: Destination identifier field in the target system.
-                - `property_mappings`: Mapping configuration as generated by ``PropertyMappingFormSet.to_property_mappings_json()``.
+                - `property_mappings`: Mapping configuration as generated by ``PropertyMappingFormSet.to_property_mappings_list()``.
         """
         raise NotImplementedError
 
@@ -270,8 +270,7 @@ class OutboundSyncProvider:
             val = ",".join(val)
         return val
 
-    def get_properties(self, inputs: dict, property_mappings: str):
-        property_mappings = json.loads(property_mappings)
+    def get_properties(self, inputs: dict, property_mappings: List[dict]):
         return [
             (m["external_field"], self.get_field_value(inputs, m), m["overwrite"])
             for m in property_mappings
diff --git a/src/pretix/base/datasync/utils.py b/src/pretix/base/datasync/utils.py
index da1f22d0de..05aab054ab 100644
--- a/src/pretix/base/datasync/utils.py
+++ b/src/pretix/base/datasync/utils.py
@@ -19,7 +19,6 @@
 # You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
 # <https://www.gnu.org/licenses/>.
 #
-import json
 from typing import List, Tuple
 
 from pretix.base.datasync.datasync import SyncConfigError
@@ -108,15 +107,17 @@ def translate_property_mappings(property_mappings, checkin_list_map):
                 om.save()
 
     """
-    mappings = json.loads(property_mappings)
+    mappings = []
 
-    for mapping in mappings:
-        if mapping["pretix_field"].startswith("checkin_date_"):
-            old_id = int(mapping["pretix_field"][len("checkin_date_"):])
+    for mapping in property_mappings:
+        pretix_field = mapping["pretix_field"]
+        if pretix_field.startswith("checkin_date_"):
+            old_id = int(pretix_field[len("checkin_date_"):])
             if old_id not in checkin_list_map:
                 # old_id might not be in checkin_list_map, because copying of an event series only copies check-in
                 # lists covering the whole series, not individual dates.
-                mapping["pretix_field"] = "_invalid_" + mapping["pretix_field"]
+                pretix_field = "_invalid_" + pretix_field
             else:
-                mapping["pretix_field"] = "checkin_date_%d" % checkin_list_map[old_id].pk
-    return json.dumps(mappings)
+                pretix_field = "checkin_date_%d" % checkin_list_map[old_id].pk
+        mappings.append({**mapping, "pretix_field": pretix_field})
+    return mappings
diff --git a/src/pretix/control/forms/mapping.py b/src/pretix/control/forms/mapping.py
index 2ff14ac274..7e48971612 100644
--- a/src/pretix/control/forms/mapping.py
+++ b/src/pretix/control/forms/mapping.py
@@ -19,8 +19,6 @@
 # You should have received a copy of the GNU Affero General Public License along with this program.  If not, see
 # <https://www.gnu.org/licenses/>.
 #
-import json
-
 from django import forms
 from django.forms import formset_factory
 from django.utils.translation import gettext_lazy as _
@@ -76,9 +74,7 @@ class PropertyMappingFormSet(formset_factory(
 )):
     template_name = "pretixcontrol/datasync/property_mappings_formset.html"
 
-    def __init__(self, pretix_fields, external_fields, available_modes, prefix, *args, initial_json=None, **kwargs):
-        if initial_json:
-            kwargs["initial"] = json.loads(initial_json)
+    def __init__(self, pretix_fields, external_fields, available_modes, prefix, *args, **kwargs):
         super().__init__(
             form_kwargs={
                 "pretix_fields": pretix_fields,
@@ -95,9 +91,9 @@ class PropertyMappingFormSet(formset_factory(
         ctx["external_fields_id"] = self.prefix + "external-fields"
         return ctx
 
-    def to_property_mappings_json(self):
+    def to_property_mappings_list(self):
         """
-        Returns a property mapping configuration as a JSON-serialized list of dictionaries.
+        Returns a property mapping configuration as a JSON-serializable list of dictionaries.
 
         Each entry specifies how to transfer data from one pretix field to one field in the external system:
 
@@ -113,7 +109,7 @@ class PropertyMappingFormSet(formset_factory(
             - `MODE_APPEND_LIST` (`"append"`) if the field is an array or a multi-select: add the value to the list.
         """
         mappings = [f.cleaned_data for f in self.ordered_forms]
-        return json.dumps(mappings)
+        return mappings
 
 
 QUESTION_TYPE_LABELS = dict(Question.TYPE_CHOICES)
diff --git a/src/tests/base/test_datasync.py b/src/tests/base/test_datasync.py
index 02c6e6ea87..aed1b93825 100644
--- a/src/tests/base/test_datasync.py
+++ b/src/tests/base/test_datasync.py
@@ -218,7 +218,7 @@ class SimpleOrderSync(OutboundSyncProvider):
                 id=1,
                 pretix_model='Order', external_object_type='ticketorders',
                 pretix_id_field='event_order_code', external_id_field='ordernumber',
-                property_mappings=json.dumps([
+                property_mappings=[
                     {
                         "pretix_field": "email",
                         "external_field": "orderemail",
@@ -249,7 +249,7 @@ class SimpleOrderSync(OutboundSyncProvider):
                         "value_map": "",
                         "overwrite": MODE_OVERWRITE,
                     },
-                ])
+                ],
             )
         ]
 
@@ -341,7 +341,7 @@ class OrderAndTicketAssociationSync(OutboundSyncProvider):
                 id=1,
                 pretix_model='OrderPosition', external_object_type='tickets',
                 pretix_id_field='ticket_id', external_id_field='ticketnumber',
-                property_mappings=json.dumps([
+                property_mappings=[
                     {
                         "pretix_field": "ticket_price",
                         "external_field": "amount",
@@ -387,14 +387,14 @@ class OrderAndTicketAssociationSync(OutboundSyncProvider):
                         }),
                         "overwrite": MODE_OVERWRITE,
                     },
-                ]),
+                ],
                 association_mappings=[],
             ),
             StaticMappingWithAssociations(
                 id=2,
                 pretix_model='Order', external_object_type='ticketorders',
                 pretix_id_field='event_order_code', external_id_field='ordernumber',
-                property_mappings=json.dumps([
+                property_mappings=[
                     {
                         "pretix_field": "email",
                         "external_field": "orderemail",
@@ -425,7 +425,7 @@ class OrderAndTicketAssociationSync(OutboundSyncProvider):
                         }),
                         "overwrite": MODE_OVERWRITE,
                     },
-                ]),
+                ],
                 association_mappings=[
                     AssociationMapping(via_mapping_id=1)
                 ],