diff --git a/src/ILLink.Tasks/build/Microsoft.NET.ILLink.Tasks.props b/src/ILLink.Tasks/build/Microsoft.NET.ILLink.Tasks.props
index d55825e7fddc..924c38b643cf 100644
--- a/src/ILLink.Tasks/build/Microsoft.NET.ILLink.Tasks.props
+++ b/src/ILLink.Tasks/build/Microsoft.NET.ILLink.Tasks.props
@@ -15,6 +15,9 @@ Copyright (c) .NET Foundation. All rights reserved.
     <!-- N.B. The ILLinkTargetsPath is used as a sentinel to indicate a version of this file has already been imported. It will also be the path
          used to import the targets later in the SDK. -->
     <ILLinkTargetsPath>$(MSBuildThisFileDirectory)Microsoft.NET.ILLink.targets</ILLinkTargetsPath>
+    <!-- Older SDKs used this property as a sentinel instead, to control the import of this file 
+         (but not the targets, which were included with the SDK). -->
+    <UsingILLinkTasksSdk>true</UsingILLinkTasksSdk>
     <ILLinkTasksAssembly Condition="'$(MSBuildRuntimeType)' == 'Core'">$(MSBuildThisFileDirectory)..\tools\net6.0\ILLink.Tasks.dll</ILLinkTasksAssembly>
     <ILLinkTasksAssembly Condition="'$(MSBuildRuntimeType)' != 'Core'">$(MSBuildThisFileDirectory)..\tools\net472\ILLink.Tasks.dll</ILLinkTasksAssembly>
   </PropertyGroup>