1 files changed, 1 insertions, 1 deletions
diff --git a/src/DotNetOpenAuth.OpenId.Provider/OpenId/Provider/RequestContract.cs b/src/DotNetOpenAuth.OpenId.Provider/OpenId/Provider/RequestContract.cs
index dee140e..ae7104c 100644
--- a/src/DotNetOpenAuth.OpenId.Provider/OpenId/Provider/RequestContract.cs
+++ b/src/DotNetOpenAuth.OpenId.Provider/OpenId/Provider/RequestContract.cs
@@ -39,7 +39,7 @@ namespace DotNetOpenAuth.OpenId.Provider {
 		/// </summary>
 		protected override IProtocolMessage ResponseMessage {
 			get {
-				Contract.Requires<InvalidOperationException>(this.IsResponseReady);
+				Requires.ValidState(this.IsResponseReady);
 				Contract.Ensures(Contract.Result<IProtocolMessage>() != null);
 				throw new NotImplementedException();
 			}