diff --git a/SMBLibrary/Client/Helpers/NTLMAuthenticationHelper.cs b/SMBLibrary/Client/Helpers/NTLMAuthenticationHelper.cs
index 51ef25b..56a5cb8 100644
--- a/SMBLibrary/Client/Helpers/NTLMAuthenticationHelper.cs
+++ b/SMBLibrary/Client/Helpers/NTLMAuthenticationHelper.cs
@@ -162,6 +162,7 @@ namespace SMBLibrary.Client
                 sessionKey = keyExchangeKey;
             }
 
+            authenticateMessage.CalculateMIC(sessionKey, negotiateMessageBytes, challengeMessageBytes);
             return authenticateMessage.GetBytes();
         }