diff --git a/src/pretix/base/datasync/datasync.py b/src/pretix/base/datasync/datasync.py
index cb5bf01b3..bc3c5bfae 100644
--- a/src/pretix/base/datasync/datasync.py
+++ b/src/pretix/base/datasync/datasync.py
@@ -90,6 +90,7 @@ StaticMapping = namedtuple('StaticMapping', ('id', 'pretix_model', 'external_obj
 
 class OutboundSyncProvider:
     max_attempts = 5
+    list_field_joiner = ","  # set to None to keep native lists in properties
 
     def __init__(self, event):
         self.event = event
@@ -281,7 +282,8 @@ class OutboundSyncProvider:
                             'Please update value mapping for field "{field_name}" - option "{val}" not assigned'
                         ).format(field_name=key, val=val)])
 
-            val = ",".join(val)
+            if self.list_field_joiner:
+                val = self.list_field_joiner.join(val)
         return val
 
     def get_properties(self, inputs: dict, property_mappings: List[dict]):
diff --git a/src/pretix/base/datasync/utils.py b/src/pretix/base/datasync/utils.py
index ecfd948c5..ebc98ca4e 100644
--- a/src/pretix/base/datasync/utils.py
+++ b/src/pretix/base/datasync/utils.py
@@ -71,15 +71,20 @@ def assign_properties(
     return out
 
 
-def _add_to_list(out, field_name, current_value, new_item, list_sep):
-    new_item = str(new_item)
+def _add_to_list(out, field_name, current_value, new_item_input, list_sep):
     if list_sep is not None:
-        new_item = new_item.replace(list_sep, "")
+        new_items = str(new_item_input).split(list_sep)
         current_value = current_value.split(list_sep) if current_value else []
-    elif not isinstance(current_value, (list, tuple)):
-        current_value = [str(current_value)]
-    if new_item not in current_value:
-        new_list = current_value + [new_item]
+    else:
+        new_items = [str(new_item_input)]
+        if not isinstance(current_value, (list, tuple)):
+            current_value = [str(current_value)]
+
+    new_list = list(current_value)
+    for new_item in new_items:
+        if new_item not in current_value:
+            new_list.append(new_item)
+    if new_list != current_value:
         if list_sep is not None:
             new_list = list_sep.join(new_list)
         out[field_name] = new_list