diff --git a/src/DaemonTests/Aggregations/rebuild_projection_with_natural_key_update.cs b/src/DaemonTests/Aggregations/rebuild_projection_with_natural_key_update.cs
new file mode 100644
index 0000000000..59da28a985
--- /dev/null
+++ b/src/DaemonTests/Aggregations/rebuild_projection_with_natural_key_update.cs
@@ -0,0 +1,101 @@
+using System;
+using System.Threading;
+using System.Threading.Tasks;
+using DaemonTests.TestingSupport;
+using JasperFx.Events;
+using JasperFx.Events.Aggregation;
+using Marten;
+using Marten.Testing.Harness;
+using Shouldly;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace DaemonTests.Aggregations;
+
+public class Bug_4966_natural_key_update_on_projection_rebuild: DaemonContext
+{
+    private const string schemaName = "rebuild_natural_key_update";
+
+    public Bug_4966_natural_key_update_on_projection_rebuild(ITestOutputHelper output) : base(output)
+    {
+    }
+
+    public sealed record ProductCode(string Value);
+
+    public sealed record ProductRegistered(Guid ProductId, string ProductCode);
+
+    public sealed record ProductCodeChanged(Guid ProductId, string NewProductCode);
+
+    public sealed record Product
+    {
+        public Guid Id { get; set; }
+
+        [NaturalKey]
+        public ProductCode Code { get; set; }
+
+        [NaturalKeySource]
+        public static Product Create(ProductRegistered e)
+        {
+            return new Product
+            {
+                Id = e.ProductId,
+                Code = new ProductCode(e.ProductCode)
+            };
+        }
+
+        [NaturalKeySource]
+        public static Product Apply(ProductCodeChanged e, Product product)
+        {
+            return product with
+            {
+                Code = new ProductCode(e.NewProductCode)
+            };
+        }
+    }
+
+    private static void ConfigureStore(StoreOptions opts)
+    {
+        opts.Connection(ConnectionSource.ConnectionString);
+        opts.DatabaseSchemaName = schemaName;
+        opts.Events.StreamIdentity = StreamIdentity.AsGuid;
+        opts.Events.AppendMode = EventAppendMode.Quick;
+        opts.Projections.Snapshot<Product>(SnapshotLifecycle.Async);
+    }
+
+
+    [Fact]
+    public async Task bug_4966_natural_key_should_be_updated_during_rebuild()
+    {
+        StoreOptions(ConfigureStore);
+        await theStore.Storage.ApplyAllConfiguredChangesToDatabaseAsync();
+        await theStore.Advanced.Clean.DeleteAllDocumentsAsync();
+        await theStore.Advanced.Clean.DeleteAllEventDataAsync();
+
+        var streamId = Guid.NewGuid();
+        var originalCode = "PROD-001";
+        var newCode = "PROD-999";
+
+        await using (var session = theStore.LightweightSession())
+        {
+            session.Events.StartStream<Product>(streamId, new ProductRegistered(streamId, originalCode));
+            await session.SaveChangesAsync();
+        }
+
+
+        await using (var session = theStore.LightweightSession())
+        {
+            session.Events.Append(streamId, new ProductCodeChanged(streamId, newCode));
+            await session.SaveChangesAsync();
+        }
+
+        var daemon = await theStore.BuildProjectionDaemonAsync();
+        await daemon.RebuildProjectionAsync<Product>(CancellationToken.None);
+
+        await using (var session = theStore.LightweightSession())
+        {
+            var product = await session.Events.FetchLatest<Product, ProductCode>(new ProductCode(newCode));
+            product.ShouldNotBeNull();
+            product.Code.Value.ShouldBe(newCode);
+        }
+    }
+}