diff --git a/src/pretix/helpers/json.py b/src/pretix/helpers/json.py
index 44e7bf180..9dc95fc09 100644
--- a/src/pretix/helpers/json.py
+++ b/src/pretix/helpers/json.py
@@ -1,3 +1,4 @@
+from django.core.files import File
 from i18nfield.utils import I18nJSONEncoder
 
 from pretix.base.reldate import RelativeDateWrapper
@@ -7,6 +8,8 @@ class CustomJSONEncoder(I18nJSONEncoder):
     def default(self, obj):
         if isinstance(obj, RelativeDateWrapper):
             return obj.to_string()
+        elif isinstance(obj, File):
+            return obj.name
         else:
             return super().default(obj)