diff --git a/Octokit/Exceptions/RepositoryFormatException.cs b/Octokit/Exceptions/RepositoryFormatException.cs
index 506fcb950f..5ee10d4ec9 100644
--- a/Octokit/Exceptions/RepositoryFormatException.cs
+++ b/Octokit/Exceptions/RepositoryFormatException.cs
@@ -3,6 +3,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.Runtime.Serialization;
+using System.Security;
 
 namespace Octokit
 {
@@ -50,7 +51,7 @@ protected RepositoryFormatException(SerializationInfo info, StreamingContext con
             if (info == null) return;
             message = info.GetString("Message");
         }
-
+        [SecurityCritical]
         public override void GetObjectData(SerializationInfo info, StreamingContext context)
         {
             base.GetObjectData(info, context);