diff --git a/src/Microsoft.Bcl.AsyncInterfaces/ref/Microsoft.Bcl.AsyncInterfaces.cs b/src/Microsoft.Bcl.AsyncInterfaces/ref/Microsoft.Bcl.AsyncInterfaces.cs
index 2bcebe391eeb..14e60e01a375 100644
--- a/src/Microsoft.Bcl.AsyncInterfaces/ref/Microsoft.Bcl.AsyncInterfaces.cs
+++ b/src/Microsoft.Bcl.AsyncInterfaces/ref/Microsoft.Bcl.AsyncInterfaces.cs
@@ -62,6 +62,11 @@ public readonly partial struct Enumerator
             public System.Runtime.CompilerServices.ConfiguredValueTaskAwaitable<bool> MoveNextAsync() { throw null; }
         }
     }
+    [System.AttributeUsageAttribute(AttributeTargets.Parameter, Inherited = false)]
+    public sealed class EnumeratorCancellationAttribute : System.Attribute
+    {
+        public EnumeratorCancellationAttribute() { }
+    }
 }
 namespace System.Threading.Tasks
 {
diff --git a/src/Microsoft.Bcl.AsyncInterfaces/src/Microsoft.Bcl.AsyncInterfaces.csproj b/src/Microsoft.Bcl.AsyncInterfaces/src/Microsoft.Bcl.AsyncInterfaces.csproj
index 710329448ba4..2a076b61760d 100644
--- a/src/Microsoft.Bcl.AsyncInterfaces/src/Microsoft.Bcl.AsyncInterfaces.csproj
+++ b/src/Microsoft.Bcl.AsyncInterfaces/src/Microsoft.Bcl.AsyncInterfaces.csproj
@@ -28,6 +28,9 @@
     <Compile Include="$(CommonPath)\CoreLib\System\Threading\Tasks\TaskAsyncEnumerableExtensions.cs">
       <Link>ProductionCode\Common\CoreLib\System\Threading\Tasks\TaskAsyncEnumerableExtensions.cs</Link>
     </Compile>
+    <Compile Include="..\..\System.Runtime\src\System\Runtime\CompilerServices\EnumeratorCancellationAttribute.cs">
+      <Link>ProductionCode\System.Runtime\src\System\Runtime\CompilerServices\EnumeratorCancellationAttribute.cs</Link>
+    </Compile>
   </ItemGroup>
   <ItemGroup Condition="'$(TargetGroup)' == 'netstandard'">
     <Reference Include="System.Runtime" />