diff --git a/CHANGELOG.md b/CHANGELOG.md
index 99198b4..23f6c22 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -35,6 +35,12 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - X10D: Removed `IEnumerable<T>.ConcatOne` - this functionality already exists with `Append`.
 
+## [3.3.1] - 2023-08-21
+
+### Fixed
+
+- X10D.Hosting: Fixed `AddHostedSingleton` not accepting an interface as the service type.
+
 ## [3.3.0] - 2023-08-21
 
 ### Added
@@ -613,7 +619,8 @@ please [open an issue](https://github.com/oliverbooth/X10D/issues)!
 
 Earlier versions of this package are undocumented and unlisted from package results.
 
-[unreleased]: https://github.com/oliverbooth/X10D/compare/v3.3.0...main
+[unreleased]: https://github.com/oliverbooth/X10D/compare/v3.3.1...main
+[3.3.1]: https://github.com/oliverbooth/X10D/releases/tag/v3.3.1
 [3.3.0]: https://github.com/oliverbooth/X10D/releases/tag/v3.3.0
 [3.2.2]: https://github.com/oliverbooth/X10D/releases/tag/v3.2.2
 [3.2.0]: https://github.com/oliverbooth/X10D/releases/tag/v3.2.0
diff --git a/X10D.Hosting/src/DependencyInjection/ServiceCollectionExtensions.cs b/X10D.Hosting/src/DependencyInjection/ServiceCollectionExtensions.cs
index 8df216c..ea0d3a4 100644
--- a/X10D.Hosting/src/DependencyInjection/ServiceCollectionExtensions.cs
+++ b/X10D.Hosting/src/DependencyInjection/ServiceCollectionExtensions.cs
@@ -29,11 +29,12 @@ public static class ServiceCollectionExtensions
     /// <typeparam name="TImplementation">The type of the implementation to use.</typeparam>
     /// <returns>A reference to this instance after the operation has completed.</returns>
     public static IServiceCollection AddHostedSingleton<TService, TImplementation>(this IServiceCollection services)
-        where TService : class, IHostedService
-        where TImplementation : class, TService
+        where TService : class
+        where TImplementation : class, TService, IHostedService
     {
         services.AddSingleton<TService, TImplementation>();
-        return services.AddSingleton<IHostedService, TService>(provider => provider.GetRequiredService<TService>());
+        return services.AddSingleton<IHostedService, TImplementation>(provider =>
+            (TImplementation)provider.GetRequiredService<TService>());
     }
 
     /// <summary>
diff --git a/X10D.Tests/src/Hosting/ServiceCollectionTests.cs b/X10D.Tests/src/Hosting/ServiceCollectionTests.cs
index 0ce3fd2..63a3db6 100644
--- a/X10D.Tests/src/Hosting/ServiceCollectionTests.cs
+++ b/X10D.Tests/src/Hosting/ServiceCollectionTests.cs
@@ -29,6 +29,27 @@ public class ServiceCollectionTests
         });
     }
 
+    [Test]
+    public void AddHostedSingleton_ShouldRegisterServiceAsSingletonAndAsHostedService_GivenServiceAndImplTypes()
+    {
+        var services = new ServiceCollection();
+
+        services.AddHostedSingleton<ITestService, TestService>();
+
+        var serviceProvider = services.BuildServiceProvider();
+        var service = serviceProvider.GetService<ITestService>();
+        var hostedService = serviceProvider.GetService<IHostedService>();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(service, Is.Not.Null);
+            Assert.That(hostedService, Is.Not.Null);
+            Assert.IsAssignableFrom<TestService>(service);
+            Assert.IsAssignableFrom<TestService>(hostedService);
+            Assert.That(hostedService, Is.SameAs(service));
+        });
+    }
+
     [Test]
     public void AddHostedSingleton_ShouldRegisterServiceTypeAsSingletonAndAsHostedService()
     {
@@ -50,8 +71,38 @@ public class ServiceCollectionTests
         });
     }
 
-    private sealed class TestService : IHostedService
+    [Test]
+    public void AddHostedSingleton_ShouldRegisterServiceTypeAsSingletonAndAsHostedService_GivenServiceAndImplTypes()
     {
+        var services = new ServiceCollection();
+
+        services.AddHostedSingleton(typeof(ITestService), typeof(TestService));
+
+        var serviceProvider = services.BuildServiceProvider();
+        var service = serviceProvider.GetService<ITestService>();
+        var hostedService = serviceProvider.GetService<IHostedService>();
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(service, Is.Not.Null);
+            Assert.That(hostedService, Is.Not.Null);
+            Assert.IsAssignableFrom<TestService>(service);
+            Assert.IsAssignableFrom<TestService>(hostedService);
+            Assert.That(hostedService, Is.SameAs(service));
+        });
+    }
+
+    private interface ITestService
+    {
+        void Foo();
+    }
+
+    private sealed class TestService : ITestService, IHostedService
+    {
+        public void Foo()
+        {
+        }
+
         public Task StartAsync(CancellationToken cancellationToken)
         {
             return Task.CompletedTask;