diff --git a/src/Build/Microsoft.Build.csproj b/src/Build/Microsoft.Build.csproj
index 2f6a8ee8a5a..a28ffe88cfd 100644
--- a/src/Build/Microsoft.Build.csproj
+++ b/src/Build/Microsoft.Build.csproj
@@ -37,9 +37,10 @@
 
     <PackageReference Include="Microsoft.IO.Redist" Condition="'$(FeatureMSIORedist)' == 'true'" />
 
+    <PackageReference Include="Microsoft.CodeAnalysis.Collections" PrivateAssets="all" />
     <PackageReference Include="Microsoft.BuildXL.Processes" Condition="'$(FeatureReportFileAccesses)' == 'true'" PrivateAssets="all" />
   </ItemGroup>
-  
+
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETFramework' and '$(DotNetBuildSourceOnly)' != 'true'">
     <PackageReference Include="Microsoft.VisualStudio.Setup.Configuration.Interop" PrivateAssets="all" />
   </ItemGroup>
diff --git a/src/Framework/Microsoft.Build.Framework.csproj b/src/Framework/Microsoft.Build.Framework.csproj
index 736cccac2f1..71087b805ca 100644
--- a/src/Framework/Microsoft.Build.Framework.csproj
+++ b/src/Framework/Microsoft.Build.Framework.csproj
@@ -13,20 +13,17 @@
     <EnablePackageValidation>true</EnablePackageValidation>
   </PropertyGroup>
 
-  <ItemGroup>
-    <PackageReference Include="Microsoft.CodeAnalysis.Collections" PrivateAssets="all" />
-  </ItemGroup>
-
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETFramework'">
+    <PackageReference Include="System.Collections.Immutable" />
     <!-- Promote CompilerServices.Unsafe from the old version we get from System.Memory on net472. -->
     <PackageReference Include="System.Runtime.CompilerServices.Unsafe" />
     <PackageReference Include="Microsoft.VisualStudio.Setup.Configuration.Interop" PrivateAssets="all" />
     <Reference Include="System.Xaml" />
   </ItemGroup>
 
+  <!-- When targeting NS2.0, make private all references not exposed in the public API. -->
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'">
-    <!-- Need Win32 API on .NET Standard to ping registry for some methods in ToolLocationHelper -->
-    <PackageReference Include="Microsoft.Win32.Registry" />
+    <PackageReference Include="System.Collections.Immutable" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup>
diff --git a/src/Tasks/Microsoft.Build.Tasks.csproj b/src/Tasks/Microsoft.Build.Tasks.csproj
index 9c4db39cb77..18a384ef6bf 100644
--- a/src/Tasks/Microsoft.Build.Tasks.csproj
+++ b/src/Tasks/Microsoft.Build.Tasks.csproj
@@ -694,11 +694,6 @@
     <Content Include="$(NuGetPackageRoot)microsoft.net.compilers.toolset\$(MicrosoftNetCompilersToolsetVersion)\tasks\net472\**\*" CopyToOutputDirectory="PreserveNewest" LinkBase="Roslyn" />
   </ItemGroup>
 
-  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'">
-    <PackageReference Include="Microsoft.Win32.Registry" />
-    <PackageReference Include="System.Reflection.Metadata" />
-  </ItemGroup>
-
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' != '.NETFramework'">
     <PackageReference Include="System.CodeDom" />
     <PackageReference Include="System.Security.Cryptography.Pkcs" />
@@ -707,6 +702,19 @@
     <Content Include="$(NuGetPackageRoot)microsoft.net.compilers.toolset\$(MicrosoftNetCompilersToolsetVersion)\tasks\netcore\**\*" CopyToOutputDirectory="PreserveNewest" LinkBase="Roslyn" />
   </ItemGroup>
 
+  <!-- When targeting NS2.0, make private all references not exposed in the public API. -->
+  <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'">
+    <ProjectReference Update="..\StringTools\StringTools.csproj" PrivateAssets="all" />
+    <PackageReference Update="System.CodeDom" PrivateAssets="all" />
+    <PackageReference Update="System.Collections.Immutable" PrivateAssets="all" />
+    <PackageReference Update="System.Resources.Extensions" PrivateAssets="all" />
+    <PackageReference Update="System.Security.Cryptography.Pkcs" PrivateAssets="all" />
+    <PackageReference Update="System.Security.Cryptography.Xml" PrivateAssets="all" />
+    <PackageReference Update="System.Threading.Tasks.Dataflow" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.Win32.Registry" PrivateAssets="all" />
+    <PackageReference Include="System.Reflection.Metadata" PrivateAssets="all" />
+  </ItemGroup>
+
   <ItemGroup>
     <!--
       Content items in this project are used to copy files to the output directory but we don't
diff --git a/src/Utilities/Microsoft.Build.Utilities.csproj b/src/Utilities/Microsoft.Build.Utilities.csproj
index 6b8153dbc9c..17a70899bc0 100644
--- a/src/Utilities/Microsoft.Build.Utilities.csproj
+++ b/src/Utilities/Microsoft.Build.Utilities.csproj
@@ -31,8 +31,13 @@
     <PackageReference Include="Microsoft.VisualStudio.Setup.Configuration.Interop" PrivateAssets="all" />
   </ItemGroup>
 
+  <!-- When targeting NS2.0, make private all references not exposed in the public API. -->
   <ItemGroup Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard'">
-    <PackageReference Include="System.Text.Encoding.CodePages" />
+    <ProjectReference Update="..\StringTools\StringTools.csproj" PrivateAssets="all" />
+    <PackageReference Update="Microsoft.IO.Redist" PrivateAssets="all" />
+    <PackageReference Update="System.Collections.Immutable" PrivateAssets="all" />
+    <PackageReference Update="System.Configuration.ConfigurationManager" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.Win32.Registry" PrivateAssets="all" />
   </ItemGroup>
 
   <ItemGroup Label="Shared Code">