diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI.Tests/Application/Authentication/MessageExtensions/MessageExtensionsAuthenticationBaseTests.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI.Tests/Application/Authentication/MessageExtensions/MessageExtensionsAuthenticationBaseTests.cs
index a3f328b60..7874e3639 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI.Tests/Application/Authentication/MessageExtensions/MessageExtensionsAuthenticationBaseTests.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI.Tests/Application/Authentication/MessageExtensions/MessageExtensionsAuthenticationBaseTests.cs
@@ -7,7 +7,7 @@
 
 namespace Microsoft.Teams.AI.Tests.Application.Authentication.MessageExtensions
 {
-    internal class MockedMessageExtensionsAuthentication : MessageExtensionsAuthenticationBase
+    internal sealed class MockedMessageExtensionsAuthentication : MessageExtensionsAuthenticationBase
     {
         private TokenResponse? _tokenExchangeResponse;
         private TokenResponse? _signInResponse;
@@ -42,12 +42,12 @@ public override Task<TokenResponse> HandleSsoTokenExchange(ITurnContext context)
         }
     }
 
-    internal class TokenExchangeRequest
+    internal sealed class TokenExchangeRequest
     {
         public Authentication? authentication { get; set; }
     }
 
-    internal class Authentication
+    internal sealed class Authentication
     {
         public string? token { get; set; }
     }
diff --git a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Application.cs b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Application.cs
index 4dc2598b6..8c757cfd3 100644
--- a/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Application.cs
+++ b/dotnet/packages/Microsoft.TeamsAI/Microsoft.TeamsAI/Application/Application.cs
@@ -859,17 +859,17 @@ private async Task _OnTurnAsync(ITurnContext turnContext, CancellationToken canc
 
                 // If user is in sign in flow, return the authentication setting name
                 string? settingName = AuthUtilities.UserInSignInFlow(turnState);
-                bool shouldStartSignIn = _startSignIn != null && await _startSignIn(turnContext, cancellationToken;
+                bool shouldStartSignIn = _startSignIn != null && await _startSignIn(turnContext, cancellationToken);
 
                 // Sign the user in
-                if (Authentication != null && (shouldStartSignIn || settingName != null))
+                if (this._authentication != null && (shouldStartSignIn || settingName != null))
                 {
                     if (settingName == null)
                     {
-                        settingName = this.Authentication.Default;
+                        settingName = this._authentication.Default;
                     }
 
-                    SignInResponse response = await Authentication.SignUserInAsync(turnContext, turnState, settingName);
+                    SignInResponse response = await this._authentication.SignUserInAsync(turnContext, turnState, settingName);
 
                     if (response.Status == SignInStatus.Complete)
                     {