diff --git a/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems b/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems
index 096397e4998e80..2db9af120d00cc 100644
--- a/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems
+++ b/src/libraries/System.Private.CoreLib/src/System.Private.CoreLib.Shared.projitems
@@ -38,6 +38,7 @@
   <PropertyGroup>
     <DefineConstants Condition="'$(TargetsUnix)' == 'true'">$(DefineConstants);TARGET_UNIX</DefineConstants>
     <DefineConstants Condition="'$(TargetsWindows)' == 'true'">$(DefineConstants);TARGET_WINDOWS</DefineConstants>
+    <DefineConstants Condition="'$(IsApplePlatform)' == 'true'">$(DefineConstants);TARGET_APPLE</DefineConstants>
     <DefineConstants Condition="'$(TargetsOSX)' == 'true'">$(DefineConstants);TARGET_OSX</DefineConstants>
     <DefineConstants Condition="'$(TargetsMacCatalyst)' == 'true'">$(DefineConstants);TARGET_MACCATALYST</DefineConstants>
     <DefineConstants Condition="'$(TargetsiOS)' == 'true'">$(DefineConstants);TARGET_IOS</DefineConstants>