diff --git a/src/Microsoft.AspNet.Hosting/WebHostBuilder.cs b/src/Microsoft.AspNet.Hosting/WebHostBuilder.cs
index 4157a831d5..5f4d3a1dd1 100644
--- a/src/Microsoft.AspNet.Hosting/WebHostBuilder.cs
+++ b/src/Microsoft.AspNet.Hosting/WebHostBuilder.cs
@@ -93,12 +93,12 @@ namespace Microsoft.AspNet.Hosting
             {
                 if (defaultPlatformServices.Application != null)
                 {
-                    services.TryAdd(ServiceDescriptor.Instance(defaultPlatformServices.Application));
+                    services.TryAddSingleton(defaultPlatformServices.Application);
                 }
 
                 if (defaultPlatformServices.Runtime != null)
                 {
-                    services.TryAdd(ServiceDescriptor.Instance(defaultPlatformServices.Runtime));
+                    services.TryAddSingleton(defaultPlatformServices.Runtime);
                 }
             }
 
diff --git a/test/Microsoft.AspNet.Hosting.Tests/Fakes/RuntimeEnvironment.cs b/test/Microsoft.AspNet.Hosting.Tests/Fakes/RuntimeEnvironment.cs
index ee180c4f01..c7cdd3f997 100644
--- a/test/Microsoft.AspNet.Hosting.Tests/Fakes/RuntimeEnvironment.cs
+++ b/test/Microsoft.AspNet.Hosting.Tests/Fakes/RuntimeEnvironment.cs
@@ -18,5 +18,7 @@ namespace Microsoft.AspNet.Hosting.Fakes
         public string RuntimeVersion { get; } = "TestRuntimeVersion";
 
         public string RuntimePath { get; } = "TestRuntimePath";
+
+        public Platform OperatingSystemPlatform => Platform.Unknown;
     }
 }