diff --git a/src/libraries/Common/src/Interop/Windows/Shell32/Interop.SHGetKnownFolderPath.cs b/src/libraries/Common/src/Interop/Windows/Shell32/Interop.SHGetKnownFolderPath.cs
index dd8226a6fc9f..136d93f8e43e 100644
--- a/src/libraries/Common/src/Interop/Windows/Shell32/Interop.SHGetKnownFolderPath.cs
+++ b/src/libraries/Common/src/Interop/Windows/Shell32/Interop.SHGetKnownFolderPath.cs
@@ -286,12 +286,6 @@ internal static class KnownFolders
             /// </summary>
             internal const string Startup = "{B97D20BB-F46A-4C97-BA10-5E3608430854}";
 
-            /// <summary>
-            /// (CSIDL_SYSTEM) System32 folder
-            /// "%windir%\system32"
-            /// </summary>
-            internal const string System = "{1AC14E77-02E7-4E5D-B744-2EB1AE5198B7}";
-
             /// <summary>
             /// (CSIDL_SYSTEMX86) X86 System32 folder
             /// "%windir%\system32" or "%windir%\syswow64"
diff --git a/src/libraries/System.ComponentModel.Composition/tests/System/ComponentModel/Composition/Hosting/AssemblyCatalogTests.cs b/src/libraries/System.ComponentModel.Composition/tests/System/ComponentModel/Composition/Hosting/AssemblyCatalogTests.cs
index 8876db46066b..da0f9cbfe84d 100644
--- a/src/libraries/System.ComponentModel.Composition/tests/System/ComponentModel/Composition/Hosting/AssemblyCatalogTests.cs
+++ b/src/libraries/System.ComponentModel.Composition/tests/System/ComponentModel/Composition/Hosting/AssemblyCatalogTests.cs
@@ -115,7 +115,7 @@ internal static void Constructor_InvalidFileNameAsCodeBaseArgument_ShouldThrowIO
 
         internal static void Constructor_DirectoryAsCodeBaseArgument_ShouldThrowFileLoad(Func<string, AssemblyCatalog> catalogCreator)
         {
-            string directory = Environment.GetFolderPath(Environment.SpecialFolder.System);
+            string directory = Environment.SystemDirectory;
             Assert.True(Directory.Exists(directory));
 
             Assert.Throws<FileLoadException>(() => catalogCreator(directory));
diff --git a/src/libraries/System.Private.CoreLib/src/System/Environment.Win32.cs b/src/libraries/System.Private.CoreLib/src/System/Environment.Win32.cs
index 10f7815ab0af..01b155d718ae 100644
--- a/src/libraries/System.Private.CoreLib/src/System/Environment.Win32.cs
+++ b/src/libraries/System.Private.CoreLib/src/System/Environment.Win32.cs
@@ -220,6 +220,14 @@ private static string GetFolderPathCore(SpecialFolder folder, SpecialFolderOptio
 
             switch (folder)
             {
+                // Special-cased values to not use SHGetFolderPath when we have a more direct option available.
+                case SpecialFolder.System:
+                    // This assumes the system directory always exists and thus we don't need to do anything special for any SpecialFolderOption.
+                    return SystemDirectory;
+                default:
+                    return string.Empty;
+
+                // Map the SpecialFolder to the appropriate Guid
                 case SpecialFolder.ApplicationData:
                     folderGuid = Interop.Shell32.KnownFolders.RoamingAppData;
                     break;
@@ -271,9 +279,6 @@ private static string GetFolderPathCore(SpecialFolder folder, SpecialFolderOptio
                 case SpecialFolder.Startup:
                     folderGuid = Interop.Shell32.KnownFolders.Startup;
                     break;
-                case SpecialFolder.System:
-                    folderGuid = Interop.Shell32.KnownFolders.System;
-                    break;
                 case SpecialFolder.Templates:
                     folderGuid = Interop.Shell32.KnownFolders.Templates;
                     break;
@@ -360,15 +365,8 @@ private static string GetFolderPathCore(SpecialFolder folder, SpecialFolderOptio
                 case SpecialFolder.Windows:
                     folderGuid = Interop.Shell32.KnownFolders.Windows;
                     break;
-                default:
-                    return string.Empty;
             }
 
-            return GetKnownFolderPath(folderGuid, option);
-        }
-
-        private static string GetKnownFolderPath(string folderGuid, SpecialFolderOption option)
-        {
             Guid folderId = new Guid(folderGuid);
 
             int hr = Interop.Shell32.SHGetKnownFolderPath(folderId, (uint)option, IntPtr.Zero, out string path);
diff --git a/src/libraries/System.Reflection.Metadata/tests/PortableExecutable/PEReaderTests.cs b/src/libraries/System.Reflection.Metadata/tests/PortableExecutable/PEReaderTests.cs
index f5358cab5a5f..20477b5a44b9 100644
--- a/src/libraries/System.Reflection.Metadata/tests/PortableExecutable/PEReaderTests.cs
+++ b/src/libraries/System.Reflection.Metadata/tests/PortableExecutable/PEReaderTests.cs
@@ -120,7 +120,7 @@ public void SubStream()
         [Fact]
         public void OpenNativeImage()
         {
-            using (var reader = new PEReader(File.OpenRead(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "kernel32.dll"))))
+            using (var reader = new PEReader(File.OpenRead(Path.Combine(Environment.SystemDirectory, "kernel32.dll"))))
             {
                 Assert.False(reader.HasMetadata);
                 Assert.True(reader.PEHeaders.IsDll);
diff --git a/src/libraries/System.Reflection/tests/AssemblyTests.cs b/src/libraries/System.Reflection/tests/AssemblyTests.cs
index 53410a35ba73..0df53d070e3f 100644
--- a/src/libraries/System.Reflection/tests/AssemblyTests.cs
+++ b/src/libraries/System.Reflection/tests/AssemblyTests.cs
@@ -402,7 +402,7 @@ public void LoadFile_PartiallyQualifiedPath_ThrowsArgumentException()
         [PlatformSpecific(TestPlatforms.Windows)]
         public void LoadFile_ValidPEBadIL_ThrowsBadImageFormatExceptionWithPath()
         {
-            string path = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.System), "kernelbase.dll");
+            string path = Path.Combine(Environment.SystemDirectory, "kernelbase.dll");
             if (!File.Exists(path))
                 return;
 
diff --git a/src/libraries/System.Runtime.Extensions/tests/System/EnvironmentTests.cs b/src/libraries/System.Runtime.Extensions/tests/System/EnvironmentTests.cs
index 55c666ba0b8b..f9ed70bd6770 100644
--- a/src/libraries/System.Runtime.Extensions/tests/System/EnvironmentTests.cs
+++ b/src/libraries/System.Runtime.Extensions/tests/System/EnvironmentTests.cs
@@ -381,17 +381,6 @@ public void GetFolderPath_Unix_SpecialFolderDoesNotExist_CreatesSuccessfully(Env
         [Fact]
         public void GetSystemDirectory()
         {
-            if (PlatformDetection.IsWindowsNanoServer)
-            {
-                // https://github.com/dotnet/runtime/issues/21430
-                // On Windows Nano, ShGetKnownFolderPath currently doesn't give
-                // the correct result for SystemDirectory.
-                // Assert that it's wrong, so that if it's fixed, we don't forget to
-                // enable this test for Nano.
-                Assert.NotEqual(Environment.GetFolderPath(Environment.SpecialFolder.System), Environment.SystemDirectory);
-                return;
-            }
-
             Assert.Equal(Environment.GetFolderPath(Environment.SpecialFolder.System), Environment.SystemDirectory);
         }