diff --git a/src/libraries/pkg/test/packageSettings/Microsoft.Windows.Compatibility/workaroundDowngrade.targets b/src/libraries/pkg/test/packageSettings/Microsoft.Windows.Compatibility/workaroundDowngrade.targets
new file mode 100644
index 0000000000000..eed2ad859c39b
--- /dev/null
+++ b/src/libraries/pkg/test/packageSettings/Microsoft.Windows.Compatibility/workaroundDowngrade.targets
@@ -0,0 +1,6 @@
+<Project>
+  <ItemGroup>
+    <!-- We cannot reference the current build of runtime.native.System.IO.Ports because its built across multiple machines -->
+    <PackageReference Condition="'$(TargetFrameworkIdentifier)' != '.NETFramework'" Include="runtime.native.System.IO.Ports" Version="$(runtimenativeSystemIOPortsVersion)" NoWarn="NU1605" />
+  </ItemGroup>
+</Project>
diff --git a/src/libraries/pkg/test/testPackages.proj b/src/libraries/pkg/test/testPackages.proj
index 83ad6233b6432..e4080b6116eb2 100644
--- a/src/libraries/pkg/test/testPackages.proj
+++ b/src/libraries/pkg/test/testPackages.proj
@@ -33,6 +33,8 @@
     </AllPackagesFilePath>
     <AllPackages Include="@(AllPackagesFilePath->'%(PackageName)')" />
 
+    <!-- runtime.native.System.IO.Ports requires all runtime legs to be built in order to test -->
+    <ExcludePackages Include="runtime.native.System.IO.Ports" />
     <ExcludePackages Condition="'$(PackagesToTest)' != ''" Include="@(AllPackages)" Exclude="@(PackagesToTest)" />
     <TestPackages Include="@(AllPackages)" Exclude="@(ExcludePackages)" />
     <TestPackagesPath Include="@(TestPackages->'%(PackagePath)')" />