diff --git a/src/Assets/TestProjects/KitchenSink/TestApp/TestApp.csproj b/src/Assets/TestProjects/KitchenSink/TestApp/TestApp.csproj
index 08c45bd4dcae..0c4bb268304d 100644
--- a/src/Assets/TestProjects/KitchenSink/TestApp/TestApp.csproj
+++ b/src/Assets/TestProjects/KitchenSink/TestApp/TestApp.csproj
@@ -26,6 +26,7 @@
     <CustomResourceTypesSupport>false</CustomResourceTypesSupport>
     <UseSystemResourceKeys>true</UseSystemResourceKeys>
     <DynamicCodeSupport>true</DynamicCodeSupport>
+    <JsonSerializerIsReflectionEnabledByDefault>false</JsonSerializerIsReflectionEnabledByDefault>
     <BuiltInComInteropSupport>false</BuiltInComInteropSupport>
     <_EnableConsumingManagedCodeFromNativeHosting>false</_EnableConsumingManagedCodeFromNativeHosting>
     <EnableCppCLIHostActivation>false</EnableCppCLIHostActivation>
diff --git a/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets b/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets
index 900ceef00e8b..4f249d77a179 100644
--- a/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets
+++ b/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.targets
@@ -558,16 +558,21 @@ Copyright (c) .NET Foundation. All rights reserved.
                                     Value="$(StartupHookSupport)"
                                     Trim="true" />
 
-    <RuntimeHostConfigurationOption Include="System.Threading.Thread.EnableAutoreleasePool"
-                                    Condition="'$(AutoreleasePoolSupport)' != ''"
-                                    Value="$(AutoreleasePoolSupport)"
-                                    Trim="true" />
-
     <RuntimeHostConfigurationOption Include="System.Text.Encoding.EnableUnsafeUTF7Encoding"
                                     Condition="'$(EnableUnsafeUTF7Encoding)' != ''"
                                     Value="$(EnableUnsafeUTF7Encoding)"
                                     Trim="true" />
 
+    <RuntimeHostConfigurationOption Include="System.Text.Json.JsonSerializer.IsReflectionEnabledByDefault"
+                                    Condition="'$(JsonSerializerIsReflectionEnabledByDefault)' != ''"
+                                    Value="$(JsonSerializerIsReflectionEnabledByDefault)"
+                                    Trim="true" />
+
+    <RuntimeHostConfigurationOption Include="System.Threading.Thread.EnableAutoreleasePool"
+                                    Condition="'$(AutoreleasePoolSupport)' != ''"
+                                    Value="$(AutoreleasePoolSupport)"
+                                    Trim="true" />
+
     <RuntimeHostConfigurationOption Include="System.Threading.ThreadPool.MinThreads"
                                     Condition="'$(ThreadPoolMinThreads)' != ''"
                                     Value="$(ThreadPoolMinThreads)" />
diff --git a/src/Tests/Microsoft.NET.Publish.Tests/GivenThatWeWantToPublishAProjectWithAllFeatures.cs b/src/Tests/Microsoft.NET.Publish.Tests/GivenThatWeWantToPublishAProjectWithAllFeatures.cs
index 0b135a68337f..1f6e624fa6ca 100644
--- a/src/Tests/Microsoft.NET.Publish.Tests/GivenThatWeWantToPublishAProjectWithAllFeatures.cs
+++ b/src/Tests/Microsoft.NET.Publish.Tests/GivenThatWeWantToPublishAProjectWithAllFeatures.cs
@@ -94,6 +94,7 @@ public void It_publishes_the_project_correctly(string targetFramework, string []
             ""System.Runtime.TieredPGO"": true,
             ""System.StartupHookProvider.IsSupported"": false,
             ""System.Text.Encoding.EnableUnsafeUTF7Encoding"": false,
+            ""System.Text.Json.JsonSerializer.IsReflectionEnabledByDefault"": false,
             ""System.Threading.Thread.EnableAutoreleasePool"": false,
             ""System.Threading.ThreadPool.MinThreads"": 2,
             ""System.Threading.ThreadPool.MaxThreads"": 9,
diff --git a/src/Tests/Microsoft.NET.Sdk.Web.Tests/PublishTests.cs b/src/Tests/Microsoft.NET.Sdk.Web.Tests/PublishTests.cs
index 2e4142f2889b..41d7514d1b49 100644
--- a/src/Tests/Microsoft.NET.Sdk.Web.Tests/PublishTests.cs
+++ b/src/Tests/Microsoft.NET.Sdk.Web.Tests/PublishTests.cs
@@ -49,6 +49,8 @@ public void TrimmingOptions_Are_Defaulted_Correctly_On_Trimmed_Apps(string targe
 
             configProperties["Microsoft.AspNetCore.EnsureJsonTrimmability"].GetValue<bool>()
                     .Should().BeTrue();
+            configProperties["System.Text.Json.JsonSerializer.IsReflectionEnabledByDefault"].GetValue<bool>()
+                    .Should().BeFalse();
         }
 
         [Theory]
@@ -81,6 +83,7 @@ public void TrimmingOptions_Are_Defaulted_Correctly_On_Aot_Apps(string targetFra
             var responseFileContents = File.ReadLines(responseFile);
 
             responseFileContents.Should().Contain("--feature:Microsoft.AspNetCore.EnsureJsonTrimmability=true");
+            responseFileContents.Should().Contain("--feature:System.Text.Json.JsonSerializer.IsReflectionEnabledByDefault=false");
             File.Exists(Path.Combine(outputDirectory, "web.config")).Should().BeFalse();
         }
 
diff --git a/src/WebSdk/ProjectSystem/Targets/Microsoft.NET.Sdk.Web.ProjectSystem.targets b/src/WebSdk/ProjectSystem/Targets/Microsoft.NET.Sdk.Web.ProjectSystem.targets
index 53deab1b0dae..c9f36f9aafb9 100644
--- a/src/WebSdk/ProjectSystem/Targets/Microsoft.NET.Sdk.Web.ProjectSystem.targets
+++ b/src/WebSdk/ProjectSystem/Targets/Microsoft.NET.Sdk.Web.ProjectSystem.targets
@@ -49,6 +49,7 @@ Copyright (c) .NET Foundation. All rights reserved.
   <PropertyGroup Condition="'$(PublishTrimmed)' == 'true' Or '$(PublishAot)' == 'true'">
     <!-- Runtime feature defaults to trim unnecessary code -->
     <EnsureAspNetCoreJsonTrimmability Condition="'$(EnsureAspNetCoreJsonTrimmability)' == ''">true</EnsureAspNetCoreJsonTrimmability>
+    <JsonSerializerIsReflectionEnabledByDefault Condition="'$(JsonSerializerIsReflectionEnabledByDefault)' == ''">false</JsonSerializerIsReflectionEnabledByDefault>
   </PropertyGroup>
 
   <!--