diff --git a/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs b/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
index 9c0fa6a75d0cf..f56404ff27024 100644
--- a/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
+++ b/src/libraries/Common/tests/TestUtilities/System/PlatformDetection.cs
@@ -50,8 +50,8 @@ public static partial class PlatformDetection
         public static bool IsThreadingSupported => !IsBrowser;
         public static bool IsBinaryFormatterSupported => !IsBrowser;
 
-        public static bool IsSpeedOptimized => !IsBrowser;
-        public static bool IsSizeOptimized => !IsSpeedOptimized;
+        public static bool IsSpeedOptimized => !IsSizeOptimized;
+        public static bool IsSizeOptimized => IsBrowser || IsAndroid || IsiOS || IstvOS;
 
         public static bool IsBrowserDomSupported => GetIsBrowserDomSupported();
         public static bool IsNotBrowserDomSupported => !IsBrowserDomSupported;
diff --git a/src/libraries/System.Linq/src/System.Linq.csproj b/src/libraries/System.Linq/src/System.Linq.csproj
index 330555dc13138..2f814694d91f5 100644
--- a/src/libraries/System.Linq/src/System.Linq.csproj
+++ b/src/libraries/System.Linq/src/System.Linq.csproj
@@ -1,8 +1,8 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
-    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser</TargetFrameworks>
+    <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-Browser;$(NetCoreAppCurrent)-Android;$(NetCoreAppCurrent)-iOS;$(NetCoreAppCurrent)-tvOS</TargetFrameworks>
     <Nullable>enable</Nullable>
-    <OptimizeForSize Condition="'$(TargetsBrowser)' == 'true'">true</OptimizeForSize>
+    <OptimizeForSize Condition="'$(TargetsBrowser)' == 'true' or '$(TargetsAndroid)' == 'true' or '$(TargetsiOS)' == 'true' or '$(TargetstvOS)' == 'true'">true</OptimizeForSize>
   </PropertyGroup>
   <ItemGroup Condition="'$(OptimizeForSize)' == true">
     <Compile Include="System\Linq\Enumerable.SizeOpt.cs" />