diff --git a/Octokit/Exceptions/RepositoryWebHookConfigException.cs b/Octokit/Exceptions/RepositoryWebHookConfigException.cs
new file mode 100644
index 00000000..2368e6c7
--- /dev/null
+++ b/Octokit/Exceptions/RepositoryWebHookConfigException.cs
@@ -0,0 +1,60 @@
+using System;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Globalization;
+using System.Linq;
+using System.Runtime.Serialization;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Octokit
+{
+#if !NETFX_CORE
+    [Serializable]
+#endif
+    [SuppressMessage("Microsoft.Design", "CA1032:ImplementStandardExceptionConstructors",
+        Justification = "These exceptions are specific to the GitHub API and not general purpose exceptions")]
+    public class RepositoryWebHookConfigException : Exception
+    {
+        readonly string message;
+
+        public RepositoryWebHookConfigException(IEnumerable<string> invalidConfig)
+        {
+            var parameterList = string.Join(", ", invalidConfig.Select(ic => ic.FromRubyCase()));
+            message = string.Format(CultureInfo.InvariantCulture,
+                "Duplicate webhook config values found - these values: {0} should not be passed in as part of the config values. Use the properties on the NewRepositoryWebHook class instead.",
+                parameterList);
+        }
+
+        public override string Message
+        {
+            get { return message; }
+        }
+
+#if !NETFX_CORE
+        /// <summary>
+        /// Constructs an instance of RepositoryWebHookConfigException
+        /// </summary>
+        /// <param name="info">
+        /// The <see cref="SerializationInfo"/> that holds the
+        /// serialized object data about the exception being thrown.
+        /// </param>
+        /// <param name="context">
+        /// The <see cref="StreamingContext"/> that contains
+        /// contextual information about the source or destination.
+        /// </param>
+        protected RepositoryWebHookConfigException(SerializationInfo info, StreamingContext context)
+            : base(info, context)
+        {
+            if (info == null) return;
+            message = info.GetString("Message");
+        }
+
+        public override void GetObjectData(SerializationInfo info, StreamingContext context)
+        {
+            base.GetObjectData(info, context);
+            info.AddValue("Message", Message);
+        }
+#endif
+    }
+}
diff --git a/Octokit/Helpers/StringExtensions.cs b/Octokit/Helpers/StringExtensions.cs
index 71df4326..f195d405 100644
--- a/Octokit/Helpers/StringExtensions.cs
+++ b/Octokit/Helpers/StringExtensions.cs
@@ -84,6 +84,17 @@ namespace Octokit
             return string.Join("_", propertyName.SplitUpperCase()).ToLowerInvariant();
         }
 
+        public static string FromRubyCase(this string propertyName)
+        {
+            Ensure.ArgumentNotNullOrEmptyString(propertyName, "s");
+            return string.Join("", propertyName.Split('_')).ToCapitalizedInvariant();
+        }
+
+        public static string ToCapitalizedInvariant(this string value)
+        {
+            Ensure.ArgumentNotNullOrEmptyString(value, "s");
+            return string.Concat(value[0].ToString().ToUpperInvariant(), value.Substring(1));
+        }
         static IEnumerable<string> SplitUpperCase(this string source)
         {
             Ensure.ArgumentNotNullOrEmptyString(source, "source");
diff --git a/Octokit/Models/Request/NewRepositoryWebHook.cs b/Octokit/Models/Request/NewRepositoryWebHook.cs
index 2c73d06c..3be98b99 100644
--- a/Octokit/Models/Request/NewRepositoryWebHook.cs
+++ b/Octokit/Models/Request/NewRepositoryWebHook.cs
@@ -62,7 +62,7 @@ namespace Octokit
         /// <param name="url">
         /// A required string defining the URL to which the payloads will be delivered.
         /// </param>
-        public NewRepositoryWebHook(string name, IReadOnlyDictionary<string, string> config, string url) 
+        public NewRepositoryWebHook(string name, IReadOnlyDictionary<string, string> config, string url)
             : base(name, config)
         {
             Ensure.ArgumentNotNullOrEmptyString(url, "url");
@@ -88,7 +88,7 @@ namespace Octokit
         /// The content type.
         /// </value>
         public WebHookContentType ContentType { get; set; }
-        
+
         /// <summary>
         /// Gets the secret used as the key for the HMAC hex digest
         /// of the body passed with the HTTP requests as an X-Hub-Signature header.
@@ -97,7 +97,7 @@ namespace Octokit
         /// The secret.
         /// </value>
         public string Secret { get; set; }
-        
+
         /// <summary>
         /// Gets whether the SSL certificate of the host will be verified when 
         /// delivering payloads. The default is `false`.
@@ -110,15 +110,30 @@ namespace Octokit
 
         public override NewRepositoryHook ToRequest()
         {
-            var config = Config.Union(new Dictionary<string, string>
+            var webHookConfig = GetWebHookConfig();
+            if (Config.Any(c => webHookConfig.ContainsKey(c.Key)))
             {
-                    { "url", Url },
-                    { "content_type", ContentType.ToParameter() },
-                    { "secret", Secret },
-                    { "insecure_ssl", InsecureSsl.ToString() }
-            }).ToDictionary(k => k.Key, v => v.Value);
+                var invalidConfigs = Config.Where(c => webHookConfig.ContainsKey(c.Key)).Select(c => c.Key);
+                throw new RepositoryWebHookConfigException(invalidConfigs);
+            }
+
+            var config = webHookConfig
+                .Union(Config, new WebHookConfigComparer())
+                .ToDictionary(k => k.Key, v => v.Value);
+
             return new NewRepositoryHook(Name, config);
         }
+
+        Dictionary<string, string> GetWebHookConfig()
+        {
+            return new Dictionary<string, string>
+            {
+                { "url", Url },
+                { "content_type", ContentType.ToParameter() },
+                { "secret", Secret },
+                { "insecure_ssl", InsecureSsl.ToString() }
+            };
+        }
     }
 
     /// <summary>
@@ -129,4 +144,17 @@ namespace Octokit
         Form,
         Json
     }
+
+    public class WebHookConfigComparer : IEqualityComparer<KeyValuePair<string, string>>
+    {
+        public bool Equals(KeyValuePair<string, string> x, KeyValuePair<string, string> y)
+        {
+            return x.Key == y.Key;
+        }
+
+        public int GetHashCode(KeyValuePair<string, string> obj)
+        {
+            return obj.Key.GetHashCode();
+        }
+    }
 }
diff --git a/Octokit/Octokit-Mono.csproj b/Octokit/Octokit-Mono.csproj
index ec28e293..4134099d 100644
--- a/Octokit/Octokit-Mono.csproj
+++ b/Octokit/Octokit-Mono.csproj
@@ -407,6 +407,7 @@
     <Compile Include="Models\Common\Committer.cs" />
     <Compile Include="Exceptions\InvalidGitIgnoreTemplateException.cs" />
     <Compile Include="Models\Request\NewRepositoryWebHook.cs" />
+    <Compile Include="Exceptions\RepositoryWebHookConfigException.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
 </Project>
\ No newline at end of file
diff --git a/Octokit/Octokit-MonoAndroid.csproj b/Octokit/Octokit-MonoAndroid.csproj
index 555f68cd..65b473d7 100644
--- a/Octokit/Octokit-MonoAndroid.csproj
+++ b/Octokit/Octokit-MonoAndroid.csproj
@@ -414,6 +414,7 @@
     <Compile Include="Models\Request\NewArbitraryMarkDown.cs" />
     <Compile Include="Exceptions\InvalidGitIgnoreTemplateException.cs" />
     <Compile Include="Models\Request\NewRepositoryWebHook.cs" />
+    <Compile Include="Exceptions\RepositoryWebHookConfigException.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath)\Novell\Novell.MonoDroid.CSharp.targets" />
 </Project>
diff --git a/Octokit/Octokit-Monotouch.csproj b/Octokit/Octokit-Monotouch.csproj
index 9ffaf4ba..9f737839 100644
--- a/Octokit/Octokit-Monotouch.csproj
+++ b/Octokit/Octokit-Monotouch.csproj
@@ -410,7 +410,8 @@
     <Compile Include="Models\Request\NewArbitraryMarkDown.cs" />
     <Compile Include="Exceptions\InvalidGitIgnoreTemplateException.cs" />
     <Compile Include="Models\Request\NewRepositoryWebHook.cs" />
+    <Compile Include="Exceptions\RepositoryWebHookConfigException.cs" />
   </ItemGroup>
   <Import Project="$(MSBuildExtensionsPath)\Xamarin\iOS\Xamarin.MonoTouch.CSharp.targets" />
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
-</Project>
+</Project>
\ No newline at end of file
diff --git a/Octokit/Octokit-Portable.csproj b/Octokit/Octokit-Portable.csproj
index 5d4fb932..61de2d7b 100644
--- a/Octokit/Octokit-Portable.csproj
+++ b/Octokit/Octokit-Portable.csproj
@@ -404,6 +404,7 @@
     <Compile Include="Models\Common\Committer.cs" />
     <Compile Include="Exceptions\InvalidGitIgnoreTemplateException.cs" />
     <Compile Include="Models\Request\NewRepositoryWebHook.cs" />
+    <Compile Include="Exceptions\RepositoryWebHookConfigException.cs" />
   </ItemGroup>
   <ItemGroup>
     <CodeAnalysisDictionary Include="..\CustomDictionary.xml">
diff --git a/Octokit/Octokit-netcore45.csproj b/Octokit/Octokit-netcore45.csproj
index c5f72441..cc584a7d 100644
--- a/Octokit/Octokit-netcore45.csproj
+++ b/Octokit/Octokit-netcore45.csproj
@@ -411,6 +411,7 @@
     <Compile Include="Models\Request\NewArbitraryMarkDown.cs" />
     <Compile Include="Exceptions\InvalidGitIgnoreTemplateException.cs" />
     <Compile Include="Models\Request\NewRepositoryWebHook.cs" />
+    <Compile Include="Exceptions\RepositoryWebHookConfigException.cs" />
   </ItemGroup>
   <ItemGroup>
     <CodeAnalysisDictionary Include="..\CustomDictionary.xml">
diff --git a/Octokit/Octokit.csproj b/Octokit/Octokit.csproj
index e559317d..c0edf9d4 100644
--- a/Octokit/Octokit.csproj
+++ b/Octokit/Octokit.csproj
@@ -76,6 +76,7 @@
     <Compile Include="Exceptions\PrivateRepositoryQuotaExceededException.cs" />
     <Compile Include="Exceptions\RepositoryExistsException.cs" />
     <Compile Include="Exceptions\RepositoryFormatException.cs" />
+    <Compile Include="Exceptions\RepositoryWebHookConfigException.cs" />
     <Compile Include="Exceptions\TwoFactorAuthorizationException.cs" />
     <Compile Include="Helpers\ApiErrorExtensions.cs" />
     <Compile Include="Helpers\ApiUrls.Authorizations.cs" />