diff --git a/src/libraries/System.IO.FileSystem/tests/FileStream/DeleteOnClose.cs b/src/libraries/System.IO.FileSystem/tests/FileStream/DeleteOnClose.cs
index 72150266a2ce0..ea32adc5352ad 100644
--- a/src/libraries/System.IO.FileSystem/tests/FileStream/DeleteOnClose.cs
+++ b/src/libraries/System.IO.FileSystem/tests/FileStream/DeleteOnClose.cs
@@ -10,6 +10,7 @@ namespace System.IO.Tests
     public class FileStream_DeleteOnClose : FileSystemTest
     {
         [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsFileLockingEnabled), nameof(PlatformDetection.IsThreadingSupported))]
+        [OuterLoop]
         public async Task OpenOrCreate_DeleteOnClose_UsableAsMutex()
         {
             var cts = new CancellationTokenSource();
@@ -69,7 +70,7 @@ public async Task OpenOrCreate_DeleteOnClose_UsableAsMutex()
             }
 
             // Wait for 1000 locks.
-            cts.CancelAfter(TimeSpan.FromSeconds(60)); // Test timeout.
+            cts.CancelAfter(TimeSpan.FromSeconds(120)); // Test timeout (reason for outerloop)
             Volatile.Write(ref locksRemaining, 500);
             await Task.WhenAll(tasks);