diff --git a/build/Rx.props b/build/Rx.props
index edff0af160..970f60e3bc 100644
--- a/build/Rx.props
+++ b/build/Rx.props
@@ -1,5 +1,7 @@
 <Project DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
   <ItemGroup>
     <PackageReference Include="System.Reactive" Version="4.1.6" />
+    <PackageReference Include="System.Threading.Tasks.Extensions" Value="4.5.3" />
+    <PackageReference Include="System.Runtime.CompilerServices.Unsafe" Value="4.6.0" />
   </ItemGroup>
 </Project>