diff --git a/src/Microsoft.AspNetCore.Server.IISIntegration/WebHostBuilderIISExtensions.cs b/src/Microsoft.AspNetCore.Server.IISIntegration/WebHostBuilderIISExtensions.cs
index c8b2da50c0..39ba3aefdf 100644
--- a/src/Microsoft.AspNetCore.Server.IISIntegration/WebHostBuilderIISExtensions.cs
+++ b/src/Microsoft.AspNetCore.Server.IISIntegration/WebHostBuilderIISExtensions.cs
@@ -20,27 +20,28 @@ namespace Microsoft.AspNetCore.Hosting
         /// Configures the port and base path the server should listen on when running behind AspNetCoreModule.
         /// The app will also be configured to capture startup errors.
         /// </summary>
-        /// <param name="app"></param>
+        /// <param name="hostBuilder"></param>
         /// <returns></returns>
-        public static IWebHostBuilder UseIISIntegration(this IWebHostBuilder app)
+        public static IWebHostBuilder UseIISIntegration(this IWebHostBuilder hostBuilder)
         {
-            if (app == null)
+            if (hostBuilder == null)
             {
-                throw new ArgumentNullException(nameof(app));
+                throw new ArgumentNullException(nameof(hostBuilder));
             }
 
-            var port = app.GetSetting(ServerPort) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPort}");
-            var path = app.GetSetting(ServerPath) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPath}");
-            var pairingToken = app.GetSetting(PairingToken) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{PairingToken}");
+            var port = hostBuilder.GetSetting(ServerPort) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPort}");
+            var path = hostBuilder.GetSetting(ServerPath) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{ServerPath}");
+            var pairingToken = hostBuilder.GetSetting(PairingToken) ?? Environment.GetEnvironmentVariable($"ASPNETCORE_{PairingToken}");
 
             if (!string.IsNullOrEmpty(port) && !string.IsNullOrEmpty(path) && !string.IsNullOrEmpty(pairingToken))
             {
                 var address = "http://localhost:" + port + path;
-                app.UseSetting(WebHostDefaults.ServerUrlsKey, address);
-                app.CaptureStartupErrors(true);
+                hostBuilder.CaptureStartupErrors(true);
 
-                app.ConfigureServices(services =>
+                hostBuilder.ConfigureServices(services =>
                 {
+                    // Delay register the url so users don't accidently overwrite it.
+                    hostBuilder.UseSetting(WebHostDefaults.ServerUrlsKey, address);
                     services.AddSingleton<IStartupFilter>(new IISSetupFilter(pairingToken));
                     services.Configure<ForwardedHeadersOptions>(options =>
                     {
@@ -56,7 +57,7 @@ namespace Microsoft.AspNetCore.Hosting
                 });
             }
 
-            return app;
+            return hostBuilder;
         }
     }
 }
diff --git a/test/Microsoft.AspNetCore.Server.IISIntegration.Tests/IISMiddlewareTests.cs b/test/Microsoft.AspNetCore.Server.IISIntegration.Tests/IISMiddlewareTests.cs
index be1aacf8b6..f2e49fb97c 100644
--- a/test/Microsoft.AspNetCore.Server.IISIntegration.Tests/IISMiddlewareTests.cs
+++ b/test/Microsoft.AspNetCore.Server.IISIntegration.Tests/IISMiddlewareTests.cs
@@ -72,6 +72,23 @@ namespace Microsoft.AspNetCore.Server.IISIntegration
             Assert.Equal(HttpStatusCode.BadRequest, response.StatusCode);
         }
 
+        [Fact]
+        public void UrlDelayRegistered()
+        {
+            var builder = new WebHostBuilder()
+                .UseSetting("TOKEN", "TestToken")
+                .UseSetting("PORT", "12345")
+                .UseSetting("APPL_PATH", "/")
+                .UseIISIntegration();
+
+            Assert.Null(builder.GetSetting(WebHostDefaults.ServerUrlsKey));
+
+            // Adds a server and calls Build()
+            var server = new TestServer(builder);
+
+            Assert.Equal("http://localhost:12345/", builder.GetSetting(WebHostDefaults.ServerUrlsKey));
+        }
+
         [Fact]
         public async Task AddsAuthenticationHandlerByDefault()
         {