diff --git a/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.Portable.csproj b/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.Portable.csproj
index 751d122c..c60697b4 100644
--- a/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.Portable.csproj
+++ b/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.Portable.csproj
@@ -76,8 +76,9 @@
       <HintPath>..\packages\NUnit.2.6.2\lib\nunit.framework.dll</HintPath>
     </Reference>
     <Reference Include="System" />
-    <Reference Include="System.Collections.Immutable">
-      <HintPath>..\packages\Microsoft.Bcl.Immutable.1.1.20-beta\lib\portable-net45+win8\System.Collections.Immutable.dll</HintPath>
+    <Reference Include="System.Collections.Immutable, Version=1.1.20.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
+      <SpecificVersion>False</SpecificVersion>
+      <HintPath>..\packages\System.Collections.Immutable.1.1.33-beta\lib\portable-net45+win8+wp8+wpa81\System.Collections.Immutable.dll</HintPath>
     </Reference>
     <Reference Include="System.ComponentModel.DataAnnotations">
       <RequiredTargetFramework>3.5</RequiredTargetFramework>
diff --git a/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.csproj b/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.csproj
index c29b6927..3b0234b0 100644
--- a/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.csproj
+++ b/Src/Newtonsoft.Json.Tests/Newtonsoft.Json.Tests.csproj
@@ -42,9 +42,9 @@
       <HintPath>..\packages\NUnit.2.6.2\lib\nunit.framework.dll</HintPath>
     </Reference>
     <Reference Include="System" />
-    <Reference Include="System.Collections.Immutable, Version=1.1.20.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
+    <Reference Include="System.Collections.Immutable, Version=1.1.33.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL">
       <SpecificVersion>False</SpecificVersion>
-      <HintPath>..\packages\Microsoft.Bcl.Immutable.1.1.20-beta\lib\portable-net45+win8\System.Collections.Immutable.dll</HintPath>
+      <HintPath>..\packages\System.Collections.Immutable.1.1.33-beta\lib\portable-net45+win8+wp8+wpa81\System.Collections.Immutable.dll</HintPath>
     </Reference>
     <Reference Include="System.ComponentModel.DataAnnotations" />
     <Reference Include="System.Core" />
@@ -427,7 +427,9 @@
       <LastGenOutput>LinqToSqlClasses.designer.cs</LastGenOutput>
       <SubType>Designer</SubType>
     </None>
-    <None Include="packages.config" />
+    <None Include="packages.config">
+      <SubType>Designer</SubType>
+    </None>
     <None Include="Schema\Specs\additionalItems.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
@@ -508,12 +510,6 @@
     <Service Include="{3259AA49-8AA1-44D3-9025-A0B520596A8C}" />
     <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
   </ItemGroup>
-  <ItemGroup>
-    <ProjectReference Include="..\Newtonsoft.Json\Newtonsoft.Json.csproj">
-      <Project>{eeea67f9-9089-481d-a4dc-0966dec9fd7d}</Project>
-      <Name>Newtonsoft.Json</Name>
-    </ProjectReference>
-  </ItemGroup>
   <ItemGroup>
     <Content Include="bunny_pancake.jpg">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
@@ -525,6 +521,12 @@
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
   </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="..\Newtonsoft.Json\Newtonsoft.Json.csproj">
+      <Project>{eeea67f9-9089-481d-a4dc-0966dec9fd7d}</Project>
+      <Name>Newtonsoft.Json</Name>
+    </ProjectReference>
+  </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
        Other similar extension points exist, see Microsoft.Common.targets.
diff --git a/Src/Newtonsoft.Json.Tests/Serialization/ImmutableCollectionsTests.cs b/Src/Newtonsoft.Json.Tests/Serialization/ImmutableCollectionsTests.cs
index 87f2fdf5..58a5ddaa 100644
--- a/Src/Newtonsoft.Json.Tests/Serialization/ImmutableCollectionsTests.cs
+++ b/Src/Newtonsoft.Json.Tests/Serialization/ImmutableCollectionsTests.cs
@@ -152,12 +152,9 @@ namespace Newtonsoft.Json.Tests.Serialization
         [Test]
         public void SerializeDefaultArray()
         {
-            ExceptionAssert.Throws<NullReferenceException>(
+            ExceptionAssert.Throws<InvalidOperationException>(
                 () => JsonConvert.SerializeObject(default(ImmutableArray<int>), Formatting.Indented),
-                new [] {
-                    "Object reference not set to an instance of an object.",
-                    "Object reference not set to an instance of an object" // mono
-                });
+                "This operation cannot be performed on a default instance of ImmutableArray<T>.  Consider initializing the array, or checking the ImmutableArray<T>.IsDefault property.");
         }
         #endregion
 
diff --git a/Src/Newtonsoft.Json.Tests/TestFixtureBase.cs b/Src/Newtonsoft.Json.Tests/TestFixtureBase.cs
index 2715dfc1..8495185b 100644
--- a/Src/Newtonsoft.Json.Tests/TestFixtureBase.cs
+++ b/Src/Newtonsoft.Json.Tests/TestFixtureBase.cs
@@ -262,9 +262,9 @@ namespace Newtonsoft.Json.Tests
 #endif
         {
 #if !NETFX_CORE
-//            CultureInfo turkey = CultureInfo.CreateSpecificCulture("tr");
-//            Thread.CurrentThread.CurrentCulture = turkey;
-//            Thread.CurrentThread.CurrentUICulture = turkey;
+            //CultureInfo turkey = CultureInfo.CreateSpecificCulture("tr");
+            //Thread.CurrentThread.CurrentCulture = turkey;
+            //Thread.CurrentThread.CurrentUICulture = turkey;
 
             Thread.CurrentThread.CurrentCulture = CultureInfo.InvariantCulture;
             Thread.CurrentThread.CurrentUICulture = CultureInfo.InvariantCulture;
diff --git a/Src/Newtonsoft.Json.Tests/packages.config b/Src/Newtonsoft.Json.Tests/packages.config
index 3161c40a..edf38072 100644
--- a/Src/Newtonsoft.Json.Tests/packages.config
+++ b/Src/Newtonsoft.Json.Tests/packages.config
@@ -2,6 +2,6 @@
 <packages>
   <package id="Autofac" version="3.5.0" targetFramework="net45" />
   <package id="FSharp.Core" version="4.0.0" targetFramework="net45" />
-  <package id="Microsoft.Bcl.Immutable" version="1.1.20-beta" targetFramework="net45" />
   <package id="NUnit" version="2.6.2" targetFramework="net45" />
+  <package id="System.Collections.Immutable" version="1.1.33-beta" targetFramework="net45" />
 </packages>
\ No newline at end of file
diff --git a/Src/NuGet.Config b/Src/NuGet.Config
index f41e9c63..1ca3f8e6 100644
--- a/Src/NuGet.Config
+++ b/Src/NuGet.Config
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
   <packageSources>
-    <add key="AspNetVNext" value="https://www.myget.org/F/aspnetvnext/api/v2" />
-    <add key="NuGet.org" value="https://nuget.org/api/v2/" />
+    <clear />
+    <add key="Offical NuGet.org" value="https://nuget.org/api/v2/" />
   </packageSources>
 </configuration>