diff --git a/.globalconfig b/.globalconfig
index 68fb0a66b2d..9856bdf9d15 100644
--- a/.globalconfig
+++ b/.globalconfig
@@ -510,6 +510,10 @@ dotnet_diagnostic.CA1846.severity = warning
 # https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1847
 dotnet_diagnostic.CA1847.severity = warning
 
+# CA1852: Seal internal types
+# https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1852
+dotnet_diagnostic.CA1852.severity = warning
+
 # CA1853: Unnecessary call to 'Dictionary.ContainsKey(key)'
 # https://learn.microsoft.com/dotnet/fundamentals/code-analysis/quality-rules/ca1853
 dotnet_diagnostic.CA1853.severity = warning
diff --git a/test/tools/TestAlc/init/Init.cs b/test/tools/TestAlc/init/Init.cs
index 4241e56fa4e..33f6635f712 100644
--- a/test/tools/TestAlc/init/Init.cs
+++ b/test/tools/TestAlc/init/Init.cs
@@ -10,7 +10,7 @@
 
 namespace Test.Isolated.Init
 {
-    internal class CustomLoadContext : AssemblyLoadContext
+    internal sealed class CustomLoadContext : AssemblyLoadContext
     {
         private readonly string _dependencyDirPath;
 
diff --git a/test/tools/TestExe/TestExe.cs b/test/tools/TestExe/TestExe.cs
index a9b3d834261..9230f9e6bff 100644
--- a/test/tools/TestExe/TestExe.cs
+++ b/test/tools/TestExe/TestExe.cs
@@ -20,7 +20,7 @@ internal enum EnvTarget
         System = 2,
     }
 
-    internal class TestExe
+    internal sealed class TestExe
     {
         private static int Main(string[] args)
         {