diff --git a/src/coreclr/tools/aot/ILCompiler/Program.cs b/src/coreclr/tools/aot/ILCompiler/Program.cs
index e9e7daa9691bad..a1530cd5dd3383 100644
--- a/src/coreclr/tools/aot/ILCompiler/Program.cs
+++ b/src/coreclr/tools/aot/ILCompiler/Program.cs
@@ -373,6 +373,7 @@ public int Run()
                     throw new CommandLineException($"Unexpected feature switch pair '{switchPair}'");
                 featureSwitches[switchAndValue[0]] = switchValue;
             }
+            featureSwitches["System.Linq.Enumerable.IsSizeOptimized"] = true;
 
             BodyAndFieldSubstitutions substitutions = default;
             IReadOnlyDictionary<ModuleDesc, IReadOnlySet<string>> resourceBlocks = default;