diff --git a/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs b/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
index c1790b0658ce64..64c2bbc309368e 100644
--- a/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
+++ b/src/libraries/System.IO.FileSystem/ref/System.IO.FileSystem.cs
@@ -23,7 +23,7 @@ public static void Delete(string path, bool recursive) { }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, System.IO.EnumerationOptions enumerationOptions) { throw null; }
         public static System.Collections.Generic.IEnumerable<string> EnumerateFileSystemEntries(string path, string searchPattern, System.IO.SearchOption searchOption) { throw null; }
-        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhen(true)] string? path) { throw null; }
+        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] string? path) { throw null; }
         public static System.DateTime GetCreationTime(string path) { throw null; }
         public static System.DateTime GetCreationTimeUtc(string path) { throw null; }
         public static string GetCurrentDirectory() { throw null; }
@@ -126,7 +126,7 @@ public static void Decrypt(string path) { }
         public static void Delete(string path) { }
         [System.Runtime.Versioning.SupportedOSPlatformAttribute("windows")]
         public static void Encrypt(string path) { }
-        public static bool Exists(string? path) { throw null; }
+        public static bool Exists([System.Diagnostics.CodeAnalysis.NotNullWhenAttribute(true)] string? path) { throw null; }
         public static System.IO.FileAttributes GetAttributes(string path) { throw null; }
         public static System.DateTime GetCreationTime(string path) { throw null; }
         public static System.DateTime GetCreationTimeUtc(string path) { throw null; }
diff --git a/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs b/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
index 4139de67fb83b9..3d02ebd98a6beb 100644
--- a/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
+++ b/src/libraries/System.IO.FileSystem/src/System/IO/Directory.cs
@@ -2,8 +2,9 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
-using System.IO;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.IO;
 using System.Linq;
 
 #if MS_IO_REDIST
@@ -49,7 +50,7 @@ public static DirectoryInfo CreateDirectory(string path)
         }
 
         // Tests if the given path refers to an existing DirectoryInfo on disk.
-        public static bool Exists(string? path)
+        public static bool Exists([NotNullWhen(true)] string? path)
         {
             try
             {