diff --git a/src/Squidex/Areas/Api/Controllers/Schemas/Models/PreviewUrlsDto.cs b/src/Squidex/Areas/Api/Controllers/Schemas/Models/PreviewUrlsDto.cs
new file mode 100644
index 000000000..39c68aef1
--- /dev/null
+++ b/src/Squidex/Areas/Api/Controllers/Schemas/Models/PreviewUrlsDto.cs
@@ -0,0 +1,15 @@
+// ==========================================================================
+//  Squidex Headless CMS
+// ==========================================================================
+//  Copyright (c) Squidex UG (haftungsbeschraenkt)
+//  All rights reserved. Licensed under the MIT license.
+// ==========================================================================
+
+using System.Collections.Generic;
+
+namespace Squidex.Areas.Api.Controllers.Schemas.Models
+{
+    public sealed class PreviewUrlsDto : Dictionary<string, string>
+    {
+    }
+}
diff --git a/src/Squidex/Areas/Api/Controllers/Schemas/Models/SchemaDetailsDto.cs b/src/Squidex/Areas/Api/Controllers/Schemas/Models/SchemaDetailsDto.cs
index e9ef7f5e0..97c9647c8 100644
--- a/src/Squidex/Areas/Api/Controllers/Schemas/Models/SchemaDetailsDto.cs
+++ b/src/Squidex/Areas/Api/Controllers/Schemas/Models/SchemaDetailsDto.cs
@@ -128,13 +128,14 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models
             foreach (var field in schema.SchemaDef.Fields)
             {
                 var fieldPropertiesDto = FieldPropertiesDtoFactory.Create(field.RawProperties);
-                var fieldDto = SimpleMapper.Map(field,
-                    new FieldDto
-                    {
-                        FieldId = field.Id,
-                        Properties = fieldPropertiesDto,
-                        Partitioning = field.Partitioning.Key
-                    });
+                var fieldDto =
+                    SimpleMapper.Map(field,
+                        new FieldDto
+                        {
+                            FieldId = field.Id,
+                            Properties = fieldPropertiesDto,
+                            Partitioning = field.Partitioning.Key
+                        });
 
                 if (field is IArrayField arrayField)
                 {
@@ -143,12 +144,13 @@ namespace Squidex.Areas.Api.Controllers.Schemas.Models
                     foreach (var nestedField in arrayField.Fields)
                     {
                         var nestedFieldPropertiesDto = FieldPropertiesDtoFactory.Create(nestedField.RawProperties);
-                        var nestedFieldDto = SimpleMapper.Map(nestedField,
-                            new NestedFieldDto
-                            {
-                                FieldId = nestedField.Id,
-                                Properties = nestedFieldPropertiesDto
-                            });
+                        var nestedFieldDto =
+                            SimpleMapper.Map(nestedField,
+                                new NestedFieldDto
+                                {
+                                    FieldId = nestedField.Id,
+                                    Properties = nestedFieldPropertiesDto
+                                });
 
                         fieldDto.Nested.Add(nestedFieldDto);
                     }
diff --git a/src/Squidex/Areas/Api/Controllers/Schemas/SchemasController.cs b/src/Squidex/Areas/Api/Controllers/Schemas/SchemasController.cs
index 1632f8e48..41af58369 100644
--- a/src/Squidex/Areas/Api/Controllers/Schemas/SchemasController.cs
+++ b/src/Squidex/Areas/Api/Controllers/Schemas/SchemasController.cs
@@ -184,9 +184,9 @@ namespace Squidex.Areas.Api.Controllers.Schemas
         [Route("apps/{app}/schemas/{name}/preview-urls")]
         [ApiPermission(Permissions.AppSchemasUpdate)]
         [ApiCosts(1)]
-        public async Task<IActionResult> PutPreviewUrls(string app, string name, [FromBody] Dictionary<string, string> request)
+        public async Task<IActionResult> PutPreviewUrls(string app, string name, [FromBody] PreviewUrlsDto request)
         {
-            await CommandBus.PublishAsync(new ConfigurePreviewUrls { PreviewUrls = request ?? new Dictionary<string, string>() });
+            await CommandBus.PublishAsync(new ConfigurePreviewUrls { PreviewUrls = request ?? new PreviewUrlsDto() });
 
             return NoContent();
         }