diff --git a/src/Microsoft.AspNet.Cors.Core/CorsOptions.cs b/src/Microsoft.AspNet.Cors.Core/CorsOptions.cs
index b460d65c20..27fe79aee8 100644
--- a/src/Microsoft.AspNet.Cors.Core/CorsOptions.cs
+++ b/src/Microsoft.AspNet.Cors.Core/CorsOptions.cs
@@ -3,8 +3,6 @@
 
 using System;
 using System.Collections.Generic;
-using Microsoft.AspNet.Cors.Core;
-using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Cors.Core
 {
@@ -22,10 +20,13 @@ namespace Microsoft.AspNet.Cors.Core
             {
                 return _defaultPolicyName;
             }
-
-            [param: NotNull]
             set
             {
+                if (value == null)
+                {
+                    throw new ArgumentNullException(nameof(value));
+                }
+
                 _defaultPolicyName = value;
             }
         }
@@ -35,8 +36,18 @@ namespace Microsoft.AspNet.Cors.Core
         /// </summary>
         /// <param name="name">The name of the policy.</param>
         /// <param name="policy">The <see cref="CorsPolicy"/> policy to be added.</param>
-        public void AddPolicy([NotNull] string name, [NotNull] CorsPolicy policy)
+        public void AddPolicy(string name, CorsPolicy policy)
         {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            if (policy == null)
+            {
+                throw new ArgumentNullException(nameof(policy));
+            }
+
             PolicyMap[name] = policy;
         }
 
@@ -45,8 +56,18 @@ namespace Microsoft.AspNet.Cors.Core
         /// </summary>
         /// <param name="name">The name of the policy.</param>
         /// <param name="configurePolicy">A delegate which can use a policy builder to build a policy.</param>
-        public void AddPolicy([NotNull] string name, [NotNull] Action<CorsPolicyBuilder> configurePolicy)
+        public void AddPolicy(string name, Action<CorsPolicyBuilder> configurePolicy)
         {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            if (configurePolicy == null)
+            {
+                throw new ArgumentNullException(nameof(configurePolicy));
+            }
+
             var policyBuilder = new CorsPolicyBuilder();
             configurePolicy(policyBuilder);
             PolicyMap[name] = policyBuilder.Build();
@@ -57,8 +78,13 @@ namespace Microsoft.AspNet.Cors.Core
         /// </summary>
         /// <param name="name">The name of the policy to lookup.</param>
         /// <returns>The <see cref="CorsPolicy"/> if the policy was added.<c>null</c> otherwise.</returns>
-        public CorsPolicy GetPolicy([NotNull] string name)
+        public CorsPolicy GetPolicy(string name)
         {
+            if (name == null)
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
             return PolicyMap.ContainsKey(name) ? PolicyMap[name] : null;
         }
     }
diff --git a/src/Microsoft.AspNet.Cors.Core/CorsPolicyBuilder.cs b/src/Microsoft.AspNet.Cors.Core/CorsPolicyBuilder.cs
index 9a5c409f77..99c1a0b795 100644
--- a/src/Microsoft.AspNet.Cors.Core/CorsPolicyBuilder.cs
+++ b/src/Microsoft.AspNet.Cors.Core/CorsPolicyBuilder.cs
@@ -4,7 +4,6 @@
 using System;
 using System.Linq;
 using Microsoft.AspNet.Cors.Core;
-using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Cors
 {
@@ -171,8 +170,13 @@ namespace Microsoft.AspNet.Cors
         /// </summary>
         /// <param name="policy">The policy which needs to be combined.</param>
         /// <returns>The current policy builder</returns>
-        private CorsPolicyBuilder Combine([NotNull] CorsPolicy policy)
+        private CorsPolicyBuilder Combine(CorsPolicy policy)
         {
+            if (policy == null)
+            {
+                throw new ArgumentNullException(nameof(policy));
+            }
+
             WithOrigins(policy.Origins.ToArray());
             WithHeaders(policy.Headers.ToArray());
             WithExposedHeaders(policy.ExposedHeaders.ToArray());
diff --git a/src/Microsoft.AspNet.Cors.Core/CorsService.cs b/src/Microsoft.AspNet.Cors.Core/CorsService.cs
index f9a2d6ea8e..de4a1cd8fc 100644
--- a/src/Microsoft.AspNet.Cors.Core/CorsService.cs
+++ b/src/Microsoft.AspNet.Cors.Core/CorsService.cs
@@ -6,7 +6,6 @@ using System.Collections.Generic;
 using System.Globalization;
 using System.Linq;
 using Microsoft.AspNet.Http;
-using Microsoft.Framework.Internal;
 using Microsoft.Framework.OptionsModel;
 using Microsoft.Framework.Primitives;
 
@@ -23,8 +22,13 @@ namespace Microsoft.AspNet.Cors.Core
         /// Creates a new instance of the <see cref="CorsService"/>.
         /// </summary>
         /// <param name="options">The option model representing <see cref="CorsOptions"/>.</param>
-        public CorsService([NotNull] IOptions<CorsOptions> options)
+        public CorsService(IOptions<CorsOptions> options)
         {
+            if (options == null)
+            {
+                throw new ArgumentNullException(nameof(options));
+            }
+
             _options = options.Value;
         }
 
@@ -36,15 +40,30 @@ namespace Microsoft.AspNet.Cors.Core
         /// <param name="policyName"></param>
         /// <returns>A <see cref="CorsResult"/> which contains the result of policy evaluation and can be
         /// used by the caller to set appropriate response headers.</returns>
-        public CorsResult EvaluatePolicy([NotNull] HttpContext context, string policyName)
+        public CorsResult EvaluatePolicy(HttpContext context, string policyName)
         {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
             var policy = _options.GetPolicy(policyName);
             return EvaluatePolicy(context, policy);
         }
 
         /// <inheritdoc />
-        public CorsResult EvaluatePolicy([NotNull] HttpContext context, [NotNull] CorsPolicy policy)
+        public CorsResult EvaluatePolicy(HttpContext context, CorsPolicy policy)
         {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
+            if (policy == null)
+            {
+                throw new ArgumentNullException(nameof(policy));
+            }
+
             var corsResult = new CorsResult();
             var accessControlRequestMethod = context.Request.Headers[CorsConstants.AccessControlRequestMethod];
             if (string.Equals(context.Request.Method, CorsConstants.PreflightHttpMethod, StringComparison.Ordinal) &&
@@ -113,6 +132,16 @@ namespace Microsoft.AspNet.Cors.Core
         /// <inheritdoc />
         public virtual void ApplyResult(CorsResult result, HttpResponse response)
         {
+            if (result == null)
+            {
+                throw new ArgumentNullException(nameof(result));
+            }
+
+            if (response == null)
+            {
+                throw new ArgumentNullException(nameof(response));
+            }
+
             var headers = response.Headers;
 
             if (result.AllowedOrigin != null)
diff --git a/src/Microsoft.AspNet.Cors.Core/CorsServiceCollectionExtensions.cs b/src/Microsoft.AspNet.Cors.Core/CorsServiceCollectionExtensions.cs
index d22dd2c855..e46363ad97 100644
--- a/src/Microsoft.AspNet.Cors.Core/CorsServiceCollectionExtensions.cs
+++ b/src/Microsoft.AspNet.Cors.Core/CorsServiceCollectionExtensions.cs
@@ -2,11 +2,8 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using Microsoft.AspNet.Cors;
 using Microsoft.AspNet.Cors.Core;
-using Microsoft.Framework.Configuration;
 using Microsoft.Framework.DependencyInjection.Extensions;
-using Microsoft.Framework.Internal;
 
 namespace Microsoft.Framework.DependencyInjection
 {
@@ -22,9 +19,19 @@ namespace Microsoft.Framework.DependencyInjection
         /// <param name="configure">A delegate which is run to configure the services.</param>
         /// <returns></returns>
         public static IServiceCollection ConfigureCors(
-            [NotNull] this IServiceCollection serviceCollection,
-            [NotNull] Action<CorsOptions> configure)
+            this IServiceCollection serviceCollection,
+            Action<CorsOptions> configure)
         {
+            if (serviceCollection == null)
+            {
+                throw new ArgumentNullException(nameof(serviceCollection));
+            }
+
+            if (configure == null)
+            {
+                throw new ArgumentNullException(nameof(configure));
+            }
+
             return serviceCollection.Configure(configure);
         }
 
diff --git a/src/Microsoft.AspNet.Cors.Core/DefaultCorsPolicyProvider.cs b/src/Microsoft.AspNet.Cors.Core/DefaultCorsPolicyProvider.cs
index e5ee17294f..188b8930fe 100644
--- a/src/Microsoft.AspNet.Cors.Core/DefaultCorsPolicyProvider.cs
+++ b/src/Microsoft.AspNet.Cors.Core/DefaultCorsPolicyProvider.cs
@@ -1,9 +1,9 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System;
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
-using Microsoft.Framework.Internal;
 using Microsoft.Framework.OptionsModel;
 
 namespace Microsoft.AspNet.Cors.Core
@@ -25,6 +25,11 @@ namespace Microsoft.AspNet.Cors.Core
         /// <inheritdoc />
         public Task<CorsPolicy> GetPolicyAsync(HttpContext context, string policyName)
         {
+            if (context == null)
+            {
+                throw new ArgumentNullException(nameof(context));
+            }
+
             return Task.FromResult(_options.GetPolicy(policyName ?? _options.DefaultPolicyName));
         }
     }
diff --git a/src/Microsoft.AspNet.Cors.Core/ICorsPolicyProvider.cs b/src/Microsoft.AspNet.Cors.Core/ICorsPolicyProvider.cs
index bc92954e9f..fa13aab7e4 100644
--- a/src/Microsoft.AspNet.Cors.Core/ICorsPolicyProvider.cs
+++ b/src/Microsoft.AspNet.Cors.Core/ICorsPolicyProvider.cs
@@ -3,7 +3,6 @@
 
 using System.Threading.Tasks;
 using Microsoft.AspNet.Http;
-using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Cors.Core
 {
@@ -18,6 +17,6 @@ namespace Microsoft.AspNet.Cors.Core
         /// <param name="context">The <see cref="HttpContext"/> associated with this call.</param>
         /// <param name="policyName">An optional policy name to look for.</param>
         /// <returns>A <see cref="CorsPolicy"/></returns>
-        Task<CorsPolicy> GetPolicyAsync([NotNull] HttpContext context, string policyName);
+        Task<CorsPolicy> GetPolicyAsync(HttpContext context, string policyName);
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Cors.Core/ICorsService.cs b/src/Microsoft.AspNet.Cors.Core/ICorsService.cs
index 5259e13493..3c94859856 100644
--- a/src/Microsoft.AspNet.Cors.Core/ICorsService.cs
+++ b/src/Microsoft.AspNet.Cors.Core/ICorsService.cs
@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using Microsoft.AspNet.Http;
-using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Cors.Core
 {
@@ -18,7 +17,7 @@ namespace Microsoft.AspNet.Cors.Core
         /// <param name="policy">The <see cref="CorsPolicy"/> which needs to be evaluated.</param>
         /// <returns>A <see cref="CorsResult"/> which contains the result of policy evaluation and can be
         /// used by the caller to set apporpriate response headers.</returns>
-        CorsResult EvaluatePolicy([NotNull] HttpContext context, [NotNull] CorsPolicy policy);
+        CorsResult EvaluatePolicy(HttpContext context, CorsPolicy policy);
 
 
         /// <summary>
@@ -26,7 +25,7 @@ namespace Microsoft.AspNet.Cors.Core
         /// </summary>
         /// <param name="result">The <see cref="CorsResult"/> used to read the allowed values.</param>
         /// <param name="response">The <see cref="HttpResponse"/> associated with the current call.</param>
-        void ApplyResult([NotNull] CorsResult result, [NotNull] HttpResponse response);
+        void ApplyResult(CorsResult result, HttpResponse response);
 
     }
 }
\ No newline at end of file
diff --git a/src/Microsoft.AspNet.Cors.Core/project.json b/src/Microsoft.AspNet.Cors.Core/project.json
index 48b267a114..6962c1be73 100644
--- a/src/Microsoft.AspNet.Cors.Core/project.json
+++ b/src/Microsoft.AspNet.Cors.Core/project.json
@@ -8,19 +8,11 @@
          "Microsoft.AspNet.Http.Extensions": "1.0.0-*",
          "Microsoft.Framework.Configuration.Abstractions": "1.0.0-*",
          "Microsoft.Framework.DependencyInjection.Abstractions": "1.0.0-*",
-         "Microsoft.Framework.NotNullAttribute.Sources": { "version": "1.0.0-*", "type": "build" },
          "Microsoft.Framework.OptionsModel": "1.0.0-*"
     },
 
     "frameworks" : {
-        "dnx451" : { 
-            "dependencies": {
-            }
-        },
-        "dnxcore50" : { 
-            "dependencies": {
-                "System.Runtime": "4.0.21-beta-*"
-            }
-        }
+        "dnx451" : { },
+        "dnxcore50" : { }
     }
 }
diff --git a/src/Microsoft.AspNet.Cors/CorsMiddleware.cs b/src/Microsoft.AspNet.Cors/CorsMiddleware.cs
index a0ef8c2ff1..cccac69fec 100644
--- a/src/Microsoft.AspNet.Cors/CorsMiddleware.cs
+++ b/src/Microsoft.AspNet.Cors/CorsMiddleware.cs
@@ -6,7 +6,6 @@ using System.Threading.Tasks;
 using Microsoft.AspNet.Builder;
 using Microsoft.AspNet.Cors.Core;
 using Microsoft.AspNet.Http;
-using Microsoft.Framework.Internal;
 using Microsoft.Framework.Primitives;
 
 namespace Microsoft.AspNet.Cors
@@ -30,11 +29,26 @@ namespace Microsoft.AspNet.Cors
         /// <param name="policyProvider">A policy provider which can get an <see cref="CorsPolicy"/>.</param>
         /// <param name="policyName">An optional name of the policy to be fetched.</param>
         public CorsMiddleware(
-            [NotNull] RequestDelegate next,
-            [NotNull] ICorsService corsService,
-            [NotNull] ICorsPolicyProvider policyProvider,
+            RequestDelegate next,
+            ICorsService corsService,
+            ICorsPolicyProvider policyProvider,
             string policyName)
         {
+            if (next == null)
+            {
+                throw new ArgumentNullException(nameof(next));
+            }
+
+            if (corsService == null)
+            {
+                throw new ArgumentNullException(nameof(corsService));
+            }
+
+            if (policyProvider == null)
+            {
+                throw new ArgumentNullException(nameof(policyProvider));
+            }
+
             _next = next;
             _corsService = corsService;
             _corsPolicyProvider = policyProvider;
@@ -48,10 +62,25 @@ namespace Microsoft.AspNet.Cors
         /// <param name="corsService">An instance of <see cref="ICorsService"/>.</param>
         /// <param name="policy">An instance of the <see cref="CorsPolicy"/> which can be applied.</param>
         public CorsMiddleware(
-           [NotNull] RequestDelegate next,
-           [NotNull] ICorsService corsService,
-           [NotNull] CorsPolicy policy)
+           RequestDelegate next,
+           ICorsService corsService,
+           CorsPolicy policy)
         {
+            if (next == null)
+            {
+                throw new ArgumentNullException(nameof(next));
+            }
+
+            if (corsService == null)
+            {
+                throw new ArgumentNullException(nameof(corsService));
+            }
+
+            if (policy == null)
+            {
+                throw new ArgumentNullException(nameof(policy));
+            }
+
             _next = next;
             _corsService = corsService;
             _policy = policy;
@@ -68,7 +97,7 @@ namespace Microsoft.AspNet.Cors
                     var corsResult = _corsService.EvaluatePolicy(context, corsPolicy);
                     _corsService.ApplyResult(corsResult, context.Response);
 
-                    var accessControlRequestMethod = 
+                    var accessControlRequestMethod =
                         context.Request.Headers[CorsConstants.AccessControlRequestMethod];
                     if (string.Equals(
                             context.Request.Method,
diff --git a/src/Microsoft.AspNet.Cors/CorsMiddlewareExtensions.cs b/src/Microsoft.AspNet.Cors/CorsMiddlewareExtensions.cs
index a66484a475..b92a22180e 100644
--- a/src/Microsoft.AspNet.Cors/CorsMiddlewareExtensions.cs
+++ b/src/Microsoft.AspNet.Cors/CorsMiddlewareExtensions.cs
@@ -2,10 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Threading.Tasks;
 using Microsoft.AspNet.Cors;
-using Microsoft.AspNet.Cors.Core;
-using Microsoft.Framework.Internal;
 
 namespace Microsoft.AspNet.Builder
 {
@@ -20,8 +17,13 @@ namespace Microsoft.AspNet.Builder
         /// <param name="app">The IApplicationBuilder passed to your Configure method</param>
         /// <param name="policyName">The policy name of a configured policy.</param>
         /// <returns>The original app parameter</returns>
-        public static IApplicationBuilder UseCors([NotNull]this IApplicationBuilder app, string policyName)
+        public static IApplicationBuilder UseCors(this IApplicationBuilder app, string policyName)
         {
+            if (app == null)
+            {
+                throw new ArgumentNullException(nameof(app));
+            }
+
             return app.UseMiddleware<CorsMiddleware>(policyName);
         }
 
@@ -32,9 +34,19 @@ namespace Microsoft.AspNet.Builder
         /// <param name="configurePolicy">A delegate which can use a policy builder to build a policy.</param>
         /// <returns>The original app parameter</returns>
         public static IApplicationBuilder UseCors(
-            [NotNull] this IApplicationBuilder app,
-            [NotNull] Action<CorsPolicyBuilder> configurePolicy)
+            this IApplicationBuilder app,
+            Action<CorsPolicyBuilder> configurePolicy)
         {
+            if (app == null)
+            {
+                throw new ArgumentNullException(nameof(app));
+            }
+
+            if (configurePolicy == null)
+            {
+                throw new ArgumentNullException(nameof(configurePolicy));
+            }
+
             var policyBuilder = new CorsPolicyBuilder();
             configurePolicy(policyBuilder);
             return app.UseMiddleware<CorsMiddleware>(policyBuilder.Build());
diff --git a/src/Microsoft.AspNet.Cors/project.json b/src/Microsoft.AspNet.Cors/project.json
index 9d0567f960..0a77b75df6 100644
--- a/src/Microsoft.AspNet.Cors/project.json
+++ b/src/Microsoft.AspNet.Cors/project.json
@@ -5,19 +5,11 @@
         "url": "https://github.com/aspnet/cors"
     },
     "dependencies": {
-        "Microsoft.AspNet.Cors.Core": "1.0.0-*",
-        "Microsoft.Framework.NotNullAttribute.Sources": { "version": "1.0.0-*", "type": "build" }
+        "Microsoft.AspNet.Cors.Core": "1.0.0-*"
     },
 
     "frameworks" : {
-        "dnx451" : { 
-            "dependencies": {
-            }
-        },
-        "dnxcore50" : { 
-            "dependencies": {
-                "System.Runtime": "4.0.21-beta-*"
-            }
-        }
+        "dnx451" : { },
+        "dnxcore50" : { }
     }
 }