diff --git a/src/Microsoft.AspNet.Hosting/Program.cs b/src/Microsoft.AspNet.Hosting/Program.cs
index 555fc241a8..6c4a24ae1c 100644
--- a/src/Microsoft.AspNet.Hosting/Program.cs
+++ b/src/Microsoft.AspNet.Hosting/Program.cs
@@ -33,10 +33,18 @@ namespace Microsoft.AspNet.Hosting
             config.AddEnvironmentVariables();
             config.AddCommandLine(args);
 
-            var engine = WebHost.CreateEngine(_serviceProvider, config)
-                .UseServer(config.Get("server"))
-                .UseStartup(config.Get("app"));
- 
+            var engine = WebHost.CreateEngine(_serviceProvider, config);
+            var server = config.Get("server");
+            if (server != null)
+            {
+                engine.UseServer(server);
+            }
+            var startup = config.Get("app");
+            if (startup != null)
+            {
+                engine.UseStartup(startup);
+            }
+
             var serverShutdown = engine.Start();
             var loggerFactory = engine.ApplicationServices.GetRequiredService<ILoggerFactory>();
             var appShutdownService = engine.ApplicationServices.GetRequiredService<IApplicationShutdown>();