diff --git a/src/Microsoft.AspNet.TestHost/ClientHandler.cs b/src/Microsoft.AspNet.TestHost/ClientHandler.cs
index 78afb19a28..add6bf48be 100644
--- a/src/Microsoft.AspNet.TestHost/ClientHandler.cs
+++ b/src/Microsoft.AspNet.TestHost/ClientHandler.cs
@@ -12,6 +12,7 @@ using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.AspNet.FeatureModel;
 using Microsoft.AspNet.Http;
+using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.TestHost
 {
@@ -28,13 +29,8 @@ namespace Microsoft.AspNet.TestHost
         /// Create a new handler.
         /// </summary>
         /// <param name="next">The pipeline entry point.</param>
-        public ClientHandler(Func<IFeatureCollection, Task> next, PathString pathBase)
+        public ClientHandler([NotNull] Func<IFeatureCollection, Task> next, PathString pathBase)
         {
-            if (next == null)
-            {
-                throw new ArgumentNullException("next");
-            }
-
             _next = next;
 
             // PathString.StartsWithSegments that we use below requires the base path to not end in a slash.
@@ -53,14 +49,9 @@ namespace Microsoft.AspNet.TestHost
         /// <param name="cancellationToken"></param>
         /// <returns></returns>
         protected override async Task<HttpResponseMessage> SendAsync(
-            HttpRequestMessage request,
+            [NotNull] HttpRequestMessage request,
             CancellationToken cancellationToken)
         {
-            if (request == null)
-            {
-                throw new ArgumentNullException("request");
-            }
-
             var state = new RequestState(request, _pathBase, cancellationToken);
             var requestContent = request.Content ?? new StreamContent(Stream.Null);
             var body = await requestContent.ReadAsStreamAsync();
diff --git a/src/Microsoft.AspNet.TestHost/RequestBuilder.cs b/src/Microsoft.AspNet.TestHost/RequestBuilder.cs
index 77344da496..3de390f63a 100644
--- a/src/Microsoft.AspNet.TestHost/RequestBuilder.cs
+++ b/src/Microsoft.AspNet.TestHost/RequestBuilder.cs
@@ -7,6 +7,7 @@ using System.Globalization;
 using System.IO;
 using System.Net.Http;
 using System.Threading.Tasks;
+using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.TestHost
 {
@@ -26,13 +27,8 @@ namespace Microsoft.AspNet.TestHost
         /// <param name="server"></param>
         /// <param name="path"></param>
         [SuppressMessage("Microsoft.Usage", "CA2234:PassSystemUriObjectsInsteadOfStrings", Justification = "Not a full URI")]
-        public RequestBuilder(TestServer server, string path)
+        public RequestBuilder([NotNull] TestServer server, string path)
         {
-            if (server == null)
-            {
-                throw new ArgumentNullException("server");
-            }
-
             _server = server;
             _req = new HttpRequestMessage(HttpMethod.Get, path);
         }
@@ -42,13 +38,8 @@ namespace Microsoft.AspNet.TestHost
         /// </summary>
         /// <param name="configure"></param>
         /// <returns></returns>
-        public RequestBuilder And(Action<HttpRequestMessage> configure)
+        public RequestBuilder And([NotNull] Action<HttpRequestMessage> configure)
         {
-            if (configure == null)
-            {
-                throw new ArgumentNullException("configure");
-            }
-
             configure(_req);
             return this;
         }
diff --git a/src/Microsoft.AspNet.TestHost/ResponseStream.cs b/src/Microsoft.AspNet.TestHost/ResponseStream.cs
index 5946117ab2..42a8a419c5 100644
--- a/src/Microsoft.AspNet.TestHost/ResponseStream.cs
+++ b/src/Microsoft.AspNet.TestHost/ResponseStream.cs
@@ -8,6 +8,7 @@ using System.Diagnostics.Contracts;
 using System.IO;
 using System.Threading;
 using System.Threading.Tasks;
+using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.TestHost
 {
@@ -28,12 +29,8 @@ namespace Microsoft.AspNet.TestHost
         private Action _onFirstWrite;
         private bool _firstWrite;
 
-        internal ResponseStream(Action onFirstWrite)
+        internal ResponseStream([NotNull] Action onFirstWrite)
         {
-            if (onFirstWrite == null)
-            {
-                throw new ArgumentNullException("onFirstWrite");
-            }
             _onFirstWrite = onFirstWrite;
             _firstWrite = true;
 
diff --git a/src/Microsoft.AspNet.TestHost/project.json b/src/Microsoft.AspNet.TestHost/project.json
index 28acab776a..c32b8f617b 100644
--- a/src/Microsoft.AspNet.TestHost/project.json
+++ b/src/Microsoft.AspNet.TestHost/project.json
@@ -2,7 +2,8 @@
     "version": "1.0.0-*",
     "description": "ASP.NET 5 web server for writing and running tests.",
     "dependencies": {
-        "Microsoft.AspNet.Hosting": "1.0.0-*"
+        "Microsoft.AspNet.Hosting": "1.0.0-*",
+        "Microsoft.Framework.NotNullAttribute.Internal": { "version": "1.0.0-*", "type": "build" }
     },
     "frameworks": {
         "dnx451": {