2 files changed, 3 insertions, 3 deletions
diff --git a/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/OpenIdProviderChannel.cs b/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/OpenIdProviderChannel.cs
index c18bcac..45a69a5 100644
--- a/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/OpenIdProviderChannel.cs
+++ b/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/OpenIdProviderChannel.cs
@@ -7,13 +7,13 @@
 namespace DotNetOpenAuth.OpenId.ChannelElements {
 	using System;
 	using System.Collections.Generic;
-	using System.Diagnostics.Contracts;
 	using System.Linq;
 	using System.Text;
 	using DotNetOpenAuth.Messaging;
 	using DotNetOpenAuth.Messaging.Bindings;
 	using DotNetOpenAuth.OpenId.Extensions;
 	using DotNetOpenAuth.OpenId.Provider;
+	using Validation;
 
 	/// <summary>
 	/// The messaging channel for OpenID Providers.
diff --git a/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/ProviderSigningBindingElement.cs b/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/ProviderSigningBindingElement.cs
index 93d86d2..fbbf37a 100644
--- a/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/ProviderSigningBindingElement.cs
+++ b/src/DotNetOpenAuth.OpenId.Provider/OpenId/ChannelElements/ProviderSigningBindingElement.cs
@@ -7,7 +7,6 @@
 namespace DotNetOpenAuth.OpenId.ChannelElements {
 	using System;
 	using System.Collections.Generic;
-	using System.Diagnostics.Contracts;
 	using System.Linq;
 	using System.Text;
 	using System.Web;
@@ -16,6 +15,7 @@ namespace DotNetOpenAuth.OpenId.ChannelElements {
 	using DotNetOpenAuth.Messaging.Reflection;
 	using DotNetOpenAuth.OpenId.Messages;
 	using DotNetOpenAuth.OpenId.Provider;
+	using Validation;
 
 	/// <summary>
 	/// The signing binding element for OpenID Providers.
@@ -217,7 +217,7 @@ namespace DotNetOpenAuth.OpenId.ChannelElements {
 		/// the inclusion and order of message parts that will be signed.
 		/// </returns>
 		private string GetSignedParameterOrder(ITamperResistantOpenIdMessage signedMessage) {
-			Requires.ValidState(this.Channel != null);
+			RequiresEx.ValidState(this.Channel != null);
 			Requires.NotNull(signedMessage, "signedMessage");
 
 			Protocol protocol = Protocol.Lookup(signedMessage.Version);