diff --git a/eng/notSupported.SourceBuild.targets b/eng/notSupported.SourceBuild.targets
deleted file mode 100644
index 743c4a3ace00bc..00000000000000
--- a/eng/notSupported.SourceBuild.targets
+++ /dev/null
@@ -1,29 +0,0 @@
-<Project>
-  <Target Name="_RedefineNotSupportedSourceFile"
-          BeforeTargets="BeforeCompile"
-          Condition="'$(DotNetBuildFromSource)' == 'true' and
-                     ('$(GeneratePlatformNotSupportedAssembly)' == 'true' or '$(GeneratePlatformNotSupportedAssemblyMessage)' != '')">
-
-    <PropertyGroup>
-      <DotNetSourceBuildIntermediatePath Condition="'$(DotNetSourceBuildIntermediatePath)' == '' and '$(ContinuousIntegrationBuild)' == 'true'">$(IntermediateOutputPath)</DotNetSourceBuildIntermediatePath>
-    </PropertyGroup>
-   
-    <Error Condition="'$(DotNetSourceBuildIntermediatePath)' == ''" 
-           Text="'DotNetSourceBuildIntermediatePath' must be specified when 'DotNetBuildFromSource' is true" />
-
-    <PropertyGroup>
-      <_notSupportedSourceDirectory>$([MSBuild]::NormalizeDirectory('$(DotNetSourceBuildIntermediatePath)', '$(MSBuildProjectName)', '$(TargetFramework)-$(TargetOS)'))</_notSupportedSourceDirectory>
-      <NotSupportedSourceFile>$(_notSupportedSourceDirectory)$(TargetName).notsupported.cs</NotSupportedSourceFile>
-    </PropertyGroup>
-
-    <MakeDir Condition="'$(DotNetBuildOffline)' != 'true'" Directories="$(_notSupportedSourceDirectory)" />
-    
-    <Error Condition="'$(DotNetBuildOffline)' == 'true' and !Exists('$(NotSupportedSourceFile)')"
-           Text="Error NotSupportedSourceFile '$(NotSupportedSourceFile)' did not exist under DotNetSourceBuildIntermediatePath." />
-
-    <!-- DotNetBuildOffline == true, don't use GenAPI and include source from DotNetSourceBuildIntermediatePath -->  
-    <ItemGroup Condition="'$(DotNetBuildOffline)' == 'true'">
-      <Compile Include="$(NotSupportedSourceFile)" />
-    </ItemGroup>
-  </Target>
-</Project>
\ No newline at end of file
diff --git a/src/libraries/Directory.Build.targets b/src/libraries/Directory.Build.targets
index 56168943651dd0..a8c203a3562025 100644
--- a/src/libraries/Directory.Build.targets
+++ b/src/libraries/Directory.Build.targets
@@ -130,13 +130,12 @@
   <Import Sdk="Microsoft.DotNet.Build.Tasks.TargetFramework.Sdk" Project="Sdk.targets" />
   <Import Project="$(RepositoryEngineeringDir)restore\repoRestore.targets" Condition="'$(DisableProjectRestore)' == 'true'" />
   <Import Project="$(RepositoryEngineeringDir)illink.targets" Condition="'$(IsSourceProject)' == 'true'" />
-  <Import Project="$(RepositoryEngineeringDir)notSupported.SourceBuild.targets" Condition="'$(DotNetBuildFromSource)' == 'true'" />
   <Import Project="$(RepositoryEngineeringDir)AvoidRestoreCycleOnSelfReference.targets" Condition="'$(AvoidRestoreCycleOnSelfReference)' == 'true'" />
 
   <ItemGroup Condition="'$(IsSourceProject)' == 'true' or '$(IsReferenceAssembly)' == 'true' or '$(IsPartialFacadeAssembly)' == 'true'">
     <PackageReference Include="Microsoft.DotNet.Build.Tasks.Packaging" Version="$(MicrosoftDotNetBuildTasksPackagingVersion)" PrivateAssets="all" IsImplicitlyDefined="true" />
     <PackageReference Include="Microsoft.DotNet.ApiCompat" Condition="'$(DotNetBuildFromSource)' != 'true'" Version="$(MicrosoftDotNetApiCompatVersion)" PrivateAssets="all" IsImplicitlyDefined="true" />
-    <PackageReference Include="Microsoft.DotNet.GenAPI" Condition="'$(DotNetBuildOffline)' != 'true'" Version="$(MicrosoftDotNetGenApiVersion)" PrivateAssets="all" IsImplicitlyDefined="true" />
+    <PackageReference Include="Microsoft.DotNet.GenAPI" Condition="'$(DotNetBuildFromSource)' != 'true'" Version="$(MicrosoftDotNetGenApiVersion)" PrivateAssets="all" IsImplicitlyDefined="true" />
     <PackageReference Include="Microsoft.DotNet.GenFacades" Version="$(MicrosoftDotNetGenFacadesVersion)" PrivateAssets="all" IsImplicitlyDefined="true" />
   </ItemGroup>