diff --git a/src/CommunityToolkit.Diagnostics/Internals/Guard.ThrowHelper.cs b/src/CommunityToolkit.Diagnostics/Internals/Guard.ThrowHelper.cs
index c76fd642d..6d28cfae4 100644
--- a/src/CommunityToolkit.Diagnostics/Internals/Guard.ThrowHelper.cs
+++ b/src/CommunityToolkit.Diagnostics/Internals/Guard.ThrowHelper.cs
@@ -60,7 +60,7 @@ public static void ThrowArgumentExceptionForIsNull<T>(T? value, string name)
         [DoesNotReturn]
         public static void ThrowArgumentNullExceptionForIsNotNull<T>(string name)
         {
-            throw new ArgumentNullException(name, $"Parameter {AssertString(name)} ({typeof(T).ToTypeString()}) must be not null).");
+            throw new ArgumentNullException(name, $"Parameter {AssertString(name)} ({typeof(T).ToTypeString()}) must be not null.");
         }
 
         /// <summary>