diff --git a/test/shared/TestApplicationErrorLogger.cs b/test/shared/TestApplicationErrorLogger.cs
index 5036f1cec9..80c12a23bd 100644
--- a/test/shared/TestApplicationErrorLogger.cs
+++ b/test/shared/TestApplicationErrorLogger.cs
@@ -2,7 +2,7 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.Collections.Generic;
+using System.Collections.Concurrent;
 using System.Linq;
 using Microsoft.AspNetCore.Server.Kestrel.Internal;
 using Microsoft.Extensions.Logging;
@@ -14,7 +14,7 @@ namespace Microsoft.AspNetCore.Testing
         // Application errors are logged using 13 as the eventId.
         private const int ApplicationErrorEventId = 13;
 
-        public List<LogMessage> Messages { get; } = new List<LogMessage>();
+        public ConcurrentBag<LogMessage> Messages { get; } = new ConcurrentBag<LogMessage>();
 
         public int TotalErrorsLogged => Messages.Count(message => message.LogLevel == LogLevel.Error);