diff --git a/Dan.Common/Extensions/HostBuilderExtensions.cs b/Dan.Common/Extensions/HostBuilderExtensions.cs
index f472a1d..3bac46b 100644
--- a/Dan.Common/Extensions/HostBuilderExtensions.cs
+++ b/Dan.Common/Extensions/HostBuilderExtensions.cs
@@ -1,6 +1,4 @@
 using System.Reflection;
-using System.Text.Json;
-using System.Text.Json.Serialization;
 using Azure.Core.Serialization;
 using Dan.Common.Interfaces;
 using Microsoft.Azure.Functions.Worker;
@@ -15,9 +13,12 @@ namespace Dan.Common.Extensions;
 public static class HostBuilderExtensions
 {
     /// <summary>
-    /// Sets up the isolated worker function with default configuration and wiring with ConfigureFunctionsWorkerDefaults(), handling application insights
-    /// logging and correct JSON serialization settings. Also adds defaults services; HttpClientFactory with a circuit-breaker enabled named client (use Constants.SafeHttpClient)
-    /// which should be used for outbound requests to the data source. Also expects to find a service implementing IEvidenceSourceMetadata.
+    ///     Sets up the isolated worker function with default configuration and wiring with ConfigureFunctionsWorkerDefaults(),
+    ///     handling application insights
+    ///     logging and correct JSON serialization settings. Also adds defaults services; HttpClientFactory with a
+    ///     circuit-breaker enabled named client (use Constants.SafeHttpClient)
+    ///     which should be used for outbound requests to the data source. Also expects to find a service implementing
+    ///     IEvidenceSourceMetadata.
     /// </summary>
     /// <param name="builder">The host builder</param>
     /// <returns>The host builder for additional chaining</returns>
@@ -25,66 +26,75 @@ public static class HostBuilderExtensions
     public static IHostBuilder ConfigureDanPluginDefaults(this IHostBuilder builder)
     {
         builder.ConfigureFunctionsWorkerDefaults(workerBuilder =>
-        {
-            workerBuilder
-                // Using preview package Microsoft.Azure.Functions.Worker.ApplicationInsights, see https://github.com/Azure/azure-functions-dotnet-worker/pull/944
-                // Requires APPLICATIONINSIGHTS_CONNECTION_STRING being set. Note that host.json logging settings will have to be replicated to worker.json
-                .AddApplicationInsights()
-                .AddApplicationInsightsLogger();
-        }, options => { options.Serializer = new NewtonsoftJsonObjectSerializer(); })
+            {
+                workerBuilder
+                    // Using preview package Microsoft.Azure.Functions.Worker.ApplicationInsights, see https://github.com/Azure/azure-functions-dotnet-worker/pull/944
+                    // Requires APPLICATIONINSIGHTS_CONNECTION_STRING being set. Note that host.json logging settings will have to be replicated to worker.json
+                    .AddApplicationInsights()
+                    .AddApplicationInsightsLogger();
+            }, options =>
+            {
+                options.Serializer = new NewtonsoftJsonObjectSerializer(
+                    // Use Newtonsoft.Json for serializing in order to support TypeNameHandling and other annotations on. This should be ported to System.Text.Json at some point.
+                    new JsonSerializerSettings
+                    {
+                        TypeNameHandling = TypeNameHandling.Auto,
+                        NullValueHandling = NullValueHandling.Ignore
+                    });
+            })
             .ConfigureServices((context, services) =>
             {
                 services.AddLogging();
                 services.AddHttpClient();
 
-                var openCircuitTimeSeconds = int.TryParse(context.Configuration["DefaultCircuitBreakerOpenCircuitTimeSeconds"], out var result) ? result : 10;
-                var failuresBeforeTripping = int.TryParse(context.Configuration["DefaultCircuitBreakerFailureBeforeTripping"], out result) ? result : 4;
+                var openCircuitTimeSeconds =
+                    int.TryParse(context.Configuration["DefaultCircuitBreakerOpenCircuitTimeSeconds"], out var result)
+                        ? result
+                        : 10;
+                var failuresBeforeTripping =
+                    int.TryParse(context.Configuration["DefaultCircuitBreakerFailureBeforeTripping"], out result)
+                        ? result
+                        : 4;
 
-                var registry = new PolicyRegistry()
+                var registry = new PolicyRegistry
                 {
                     {
                         Constants.SafeHttpClientPolicy,
                         HttpPolicyExtensions.HandleTransientHttpError()
                             .CircuitBreakerAsync(
-                                handledEventsAllowedBeforeBreaking: failuresBeforeTripping,
-                                durationOfBreak: TimeSpan.FromSeconds(openCircuitTimeSeconds))
+                                failuresBeforeTripping,
+                                TimeSpan.FromSeconds(openCircuitTimeSeconds))
                     }
                 };
                 services.AddPolicyRegistry(registry);
 
-                var httpClientTimeoutSeconds = int.TryParse(context.Configuration["SafeHttpClientTimeout"], out result) ? result : 30;
+                var httpClientTimeoutSeconds = int.TryParse(context.Configuration["SafeHttpClientTimeout"], out result)
+                    ? result
+                    : 30;
 
                 // Client configured with circuit breaker policies
                 services.AddHttpClient(Constants.SafeHttpClient,
                         client => { client.Timeout = TimeSpan.FromSeconds(httpClientTimeoutSeconds); })
                     .AddPolicyHandlerFromRegistry(Constants.SafeHttpClientPolicy);
 
-                services.Configure<JsonSerializerOptions>(options =>
-                {
-                    options.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
-                    options.DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull;
-                    options.Converters.Add(new JsonStringEnumConverter());
-                });
-
-                // Try to add the first IEvidenceSourceMetadata implementation we can find
+                // Try to add the first IEvidenceSourceMetadata implementation we can find in the entry assembly
                 var evidenceSourceMetadataServiceType = typeof(IEvidenceSourceMetadata);
-                var assembly = Assembly.GetExecutingAssembly();
+                var assembly = Assembly.GetEntryAssembly();
 
-                var implementationType = assembly.GetTypes()
-                   .FirstOrDefault(t => t.GetInterfaces().Any(i => i == evidenceSourceMetadataServiceType));
+                var implementationType = assembly?.GetTypes()
+                    .FirstOrDefault(t => t.GetInterfaces().Any(i => i == evidenceSourceMetadataServiceType));
 
                 if (implementationType == null)
-                {
                     throw new NotImplementedException(
-                        $"Missing implementation of {nameof(IEvidenceSourceMetadata)}");
-                }
+                        $"Missing implementation of {nameof(IEvidenceSourceMetadata)} in entry assembly {assembly?.FullName ?? "(unmanaged assembly)"}");
 
-                if (!services.Any(s => s.ServiceType == evidenceSourceMetadataServiceType && s.ImplementationType == implementationType))
-                {
-                    services.Add(new ServiceDescriptor(evidenceSourceMetadataServiceType, implementationType, ServiceLifetime.Singleton));
-                }
+                if (!services.Any(s =>
+                        s.ServiceType == evidenceSourceMetadataServiceType &&
+                        s.ImplementationType == implementationType))
+                    services.Add(new ServiceDescriptor(evidenceSourceMetadataServiceType, implementationType,
+                        ServiceLifetime.Singleton));
             });
 
         return builder;
     }
-}
+}
\ No newline at end of file