diff --git a/src/DotNetCore.CAP/CAP.ServiceCollectionExtensions.cs b/src/DotNetCore.CAP/CAP.ServiceCollectionExtensions.cs
index 826f3ba..cfb1fad 100644
--- a/src/DotNetCore.CAP/CAP.ServiceCollectionExtensions.cs
+++ b/src/DotNetCore.CAP/CAP.ServiceCollectionExtensions.cs
@@ -37,6 +37,8 @@ namespace Microsoft.Extensions.DependencyInjection
             services.TryAddSingleton<IMessagePacker, DefaultMessagePacker>();
             services.TryAddSingleton<IConsumerServiceSelector, DefaultConsumerServiceSelector>();
             services.TryAddSingleton<IModelBinderFactory, ModelBinderFactory>();
+
+            services.TryAddSingleton<ICallbackMessageSender, CallbackMessageSender>();
             services.TryAddSingleton<IConsumerInvokerFactory, ConsumerInvokerFactory>();
             services.TryAddSingleton<MethodMatcherCache>();