diff --git a/CHANGELOG.md b/CHANGELOG.md
index 049c0f363..829cc6749 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## VNext
 - [Populate required field Message with "n/a" if it is empty](https://github.com/microsoft/ApplicationInsights-dotnet/issues/1066)
+- [Fix ITelemetryModule singleton registration to support presence of keyed services](https://github.com/microsoft/ApplicationInsights-dotnet/pull/2908)
 
 ## Version 2.22.0
 - no changes since beta.
diff --git a/NETCORE/src/Shared/Extensions/ApplicationInsightsExtensions.cs b/NETCORE/src/Shared/Extensions/ApplicationInsightsExtensions.cs
index efbce45c4..e726712e2 100644
--- a/NETCORE/src/Shared/Extensions/ApplicationInsightsExtensions.cs
+++ b/NETCORE/src/Shared/Extensions/ApplicationInsightsExtensions.cs
@@ -312,7 +312,7 @@
         private static void AddCommonTelemetryModules(IServiceCollection services)
         {
             // Previously users were encouraged to manually add the DiagnosticsTelemetryModule.
-            services.TryAddSingleton<ITelemetryModule, DiagnosticsTelemetryModule>();
+            services.TryAddEnumerable(ServiceDescriptor.Singleton<ITelemetryModule, DiagnosticsTelemetryModule>());
 
             // These modules add properties to Heartbeat and expect the DiagnosticsTelemetryModule to be configured in DI.
             services.AddSingleton<ITelemetryModule, AppServicesHeartbeatTelemetryModule>();
diff --git a/NETCORE/test/Microsoft.ApplicationInsights.AspNetCore.Tests/Extensions/ApplicationInsightsExtensionsTests/AddApplicationInsightsTelemetryTests.cs b/NETCORE/test/Microsoft.ApplicationInsights.AspNetCore.Tests/Extensions/ApplicationInsightsExtensionsTests/AddApplicationInsightsTelemetryTests.cs
index 69956615d..01e4c027c 100644
--- a/NETCORE/test/Microsoft.ApplicationInsights.AspNetCore.Tests/Extensions/ApplicationInsightsExtensionsTests/AddApplicationInsightsTelemetryTests.cs
+++ b/NETCORE/test/Microsoft.ApplicationInsights.AspNetCore.Tests/Extensions/ApplicationInsightsExtensionsTests/AddApplicationInsightsTelemetryTests.cs
@@ -37,14 +37,22 @@ namespace Microsoft.Extensions.DependencyInjection.Test
 
     public class AddApplicationInsightsTelemetryTests : BaseTestClass
     {
-        [Fact]
-        public static void TelemetryModulesResolvableWhenKeyedServiceRegistered()
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public static void TelemetryModulesResolvableWhenKeyedServiceRegistered(bool manuallyRegisterDiagnosticsTelemetryModule)
         {
             // Note: This test verifies a regression doesn't get introduced for:
-            // https://github.com/dotnet/extensions/issues/5222
+            // https://github.com/microsoft/ApplicationInsights-dotnet/issues/2879
 
             var services = new ServiceCollection();
 
+            services.AddSingleton<ITelemetryModule, TestTelemetryModule>();
+            if (manuallyRegisterDiagnosticsTelemetryModule)
+            {
+                services.AddSingleton<ITelemetryModule, DiagnosticsTelemetryModule>();
+            }
+
             services.AddKeyedSingleton(typeof(ITestService), serviceKey: new(), implementationType: typeof(TestService));
             services.AddKeyedSingleton(typeof(ITestService), serviceKey: new(), implementationInstance: new TestService());
             services.AddKeyedSingleton(typeof(ITestService), serviceKey: new(), implementationFactory: (sp, key) => new TestService());
@@ -55,7 +63,9 @@ namespace Microsoft.Extensions.DependencyInjection.Test
 
             var telemetryModules = sp.GetServices<ITelemetryModule>();
 
-            Assert.Equal(7, telemetryModules.Count());
+            Assert.Equal(8, telemetryModules.Count());
+
+            Assert.Single(telemetryModules.Where(m => m.GetType() == typeof(DiagnosticsTelemetryModule)));
         }
 
         [Theory]
diff --git a/NETCORE/test/Microsoft.ApplicationInsights.WorkerService.Tests/ExtensionsTest.cs b/NETCORE/test/Microsoft.ApplicationInsights.WorkerService.Tests/ExtensionsTest.cs
index d4503e9f1..f0d5661c8 100644
--- a/NETCORE/test/Microsoft.ApplicationInsights.WorkerService.Tests/ExtensionsTest.cs
+++ b/NETCORE/test/Microsoft.ApplicationInsights.WorkerService.Tests/ExtensionsTest.cs
@@ -123,14 +123,22 @@ namespace Microsoft.ApplicationInsights.WorkerService.Tests
             return services;
         }
 
-        [Fact]
-        public static void TelemetryModulesResolvableWhenKeyedServiceRegistered()
+        [Theory]
+        [InlineData(true)]
+        [InlineData(false)]
+        public static void TelemetryModulesResolvableWhenKeyedServiceRegistered(bool manuallyRegisterDiagnosticsTelemetryModule)
         {
             // Note: This test verifies a regression doesn't get introduced for:
-            // https://github.com/dotnet/extensions/issues/5222
+            // https://github.com/microsoft/ApplicationInsights-dotnet/issues/2879
 
             var services = new ServiceCollection();
 
+            services.AddSingleton<ITelemetryModule, TestTelemetryModule>();
+            if (manuallyRegisterDiagnosticsTelemetryModule)
+            {
+                services.AddSingleton<ITelemetryModule, DiagnosticsTelemetryModule>();
+            }
+
             services.AddKeyedSingleton(typeof(ITestService), serviceKey: new(), implementationType: typeof(TestService));
             services.AddKeyedSingleton(typeof(ITestService), serviceKey: new(), implementationInstance: new TestService());
             services.AddKeyedSingleton(typeof(ITestService), serviceKey: new(), implementationFactory: (sp, key) => new TestService());
@@ -141,7 +149,9 @@ namespace Microsoft.ApplicationInsights.WorkerService.Tests
 
             var telemetryModules = sp.GetServices<ITelemetryModule>();
 
-            Assert.Equal(7, telemetryModules.Count());
+            Assert.Equal(8, telemetryModules.Count());
+
+            Assert.Single(telemetryModules.Where(m => m.GetType() == typeof(DiagnosticsTelemetryModule)));
         }
 
         [Theory]
@@ -921,6 +931,13 @@ namespace Microsoft.ApplicationInsights.WorkerService.Tests
         {
         }
 
+        private sealed class TestTelemetryModule : ITelemetryModule
+        {
+            public void Initialize(TelemetryConfiguration configuration)
+            {
+            }
+        }
+
         private interface ITestService
         {
         }