2 files changed, 2 insertions, 2 deletions
diff --git a/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/MessageBase.cs b/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/MessageBase.cs
index e966376..272b690 100644
--- a/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/MessageBase.cs
+++ b/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/MessageBase.cs
@@ -8,8 +8,8 @@ namespace DotNetOpenAuth.OAuth2.Messages {
 	using System;
 	using System.Collections.Generic;
 	using System.Diagnostics.CodeAnalysis;
-	using System.Diagnostics.Contracts;
 	using DotNetOpenAuth.Messaging;
+	using Validation;
 
 	/// <summary>
 	/// A common message base class for OAuth messages.
diff --git a/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/UnauthorizedResponse.cs b/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/UnauthorizedResponse.cs
index e4a8a48..d90d1b5 100644
--- a/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/UnauthorizedResponse.cs
+++ b/src/DotNetOpenAuth.OAuth2/OAuth2/Messages/UnauthorizedResponse.cs
@@ -7,12 +7,12 @@
 namespace DotNetOpenAuth.OAuth2.Messages {
 	using System;
 	using System.Collections.Generic;
-	using System.Diagnostics.Contracts;
 	using System.Globalization;
 	using System.Net;
 	using System.Text;
 	using DotNetOpenAuth.Messaging;
 	using DotNetOpenAuth.OAuth2.ChannelElements;
+	using Validation;
 
 	/// <summary>
 	/// A direct response sent in response to a rejected Bearer access token.