diff --git a/src/Umbraco.Core/Models/DeliveryApi/ApiElement.cs b/src/Umbraco.Core/Models/DeliveryApi/ApiElement.cs
index b7d10814fc..d5941a1ed1 100644
--- a/src/Umbraco.Core/Models/DeliveryApi/ApiElement.cs
+++ b/src/Umbraco.Core/Models/DeliveryApi/ApiElement.cs
@@ -1,3 +1,5 @@
+using System.Text.Json.Serialization;
+
 namespace Umbraco.Cms.Core.Models.DeliveryApi;
 
 public class ApiElement : IApiElement
@@ -11,6 +13,9 @@ public class ApiElement : IApiElement
 
     public Guid Id { get; }
 
+    // Ensure the ContentType property is serialized first
+    // This is needed so it can be used as a discriminator field by System.Text.Json
+    [JsonPropertyOrder(-100)]
     public string ContentType { get; }
 
     public IDictionary<string, object?> Properties { get; }
diff --git a/src/Umbraco.Core/Models/DeliveryApi/IApiElement.cs b/src/Umbraco.Core/Models/DeliveryApi/IApiElement.cs
index 7630225f64..e62525aa34 100644
--- a/src/Umbraco.Core/Models/DeliveryApi/IApiElement.cs
+++ b/src/Umbraco.Core/Models/DeliveryApi/IApiElement.cs
@@ -1,9 +1,14 @@
+using System.Text.Json.Serialization;
+
 namespace Umbraco.Cms.Core.Models.DeliveryApi;
 
 public interface IApiElement
 {
     Guid Id { get; }
 
+    // Ensure the ContentType property is serialized first
+    // This is needed so it can be used as a discriminator field by System.Text.Json
+    [JsonPropertyOrder(-100)]
     string ContentType { get; }
 
     IDictionary<string, object?> Properties { get; }
diff --git a/src/Umbraco.Infrastructure/PropertyEditors/ValueConverters/BlockListPropertyValueConverter.cs b/src/Umbraco.Infrastructure/PropertyEditors/ValueConverters/BlockListPropertyValueConverter.cs
index 334b1f1aa3..52efe3755a 100644
--- a/src/Umbraco.Infrastructure/PropertyEditors/ValueConverters/BlockListPropertyValueConverter.cs
+++ b/src/Umbraco.Infrastructure/PropertyEditors/ValueConverters/BlockListPropertyValueConverter.cs
@@ -113,7 +113,7 @@ public class BlockListPropertyValueConverter : BlockPropertyValueConverterBase<B
 
     /// <inheritdoc />
     public Type GetDeliveryApiPropertyValueType(IPublishedPropertyType propertyType)
-        => typeof(IEnumerable<ApiBlockListModel>);
+        => typeof(ApiBlockListModel);
 
     /// <inheritdoc />
     public object? ConvertIntermediateToDeliveryApiObject(IPublishedElement owner, IPublishedPropertyType propertyType, PropertyCacheLevel referenceCacheLevel, object? inter, bool preview, bool expanding)