diff --git a/src/ApplicationCore/Types.cs b/src/ApplicationCore/Types.cs
index 23af3b2..5a2a872 100644
--- a/src/ApplicationCore/Types.cs
+++ b/src/ApplicationCore/Types.cs
@@ -1,4 +1,4 @@
-using Ardalis.GuardClauses;
+using System;
 
 namespace Microsoft.eShopWeb;
 
@@ -8,7 +8,11 @@
     
     public Username(string value)
     {
-        Guard.Against.NullOrEmpty(value);
+        if (string.IsNullOrEmpty(value))
+        {
+            throw new ArgumentNullException(nameof(value));
+        }
+        
         Value = value;
     }