diff --git a/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet6_0.verified.md b/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet6_0.verified.md
index 2982372..67bf1bb 100644
--- a/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet6_0.verified.md
+++ b/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet6_0.verified.md
@@ -93,7 +93,7 @@
    ) : void [NullableContext, AssertionMethod, ContractAnnotation]
  - Fail.IfArgumentWhiteSpace(
      argumentValue: string [CanBeNull, AssertionCondition],
-     argumentName: string [NotNull, NotNull]
+     argumentName: string? [Nullable, CallerArgumentExpression, Optional]
    ) : void [AssertionMethod, ContractAnnotation]
  - Fail.IfCollectionContains<T>(
      collection: IEnumerable<T> [CanBeNull, AssertionCondition],
diff --git a/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet7_0.verified.md b/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet7_0.verified.md
index 501cd40..9d9e0d5 100644
--- a/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet7_0.verified.md
+++ b/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet7_0.verified.md
@@ -93,7 +93,7 @@
    ) : void [NullableContext, AssertionMethod, ContractAnnotation]
  - Fail.IfArgumentWhiteSpace(
      argumentValue: string [CanBeNull, AssertionCondition],
-     argumentName: string [NotNull, NotNull]
+     argumentName: string? [Nullable, CallerArgumentExpression, Optional]
    ) : void [AssertionMethod, ContractAnnotation]
  - Fail.IfCollectionContains<T>(
      collection: IEnumerable<T> [CanBeNull, AssertionCondition],
diff --git a/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet8_0.verified.md b/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet8_0.verified.md
index 501cd40..9d9e0d5 100644
--- a/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet8_0.verified.md
+++ b/Contracts/Synergy.Contracts.Test/Architecture/Public/Api.of.Synergy.Contracts.DotNet8_0.verified.md
@@ -93,7 +93,7 @@
    ) : void [NullableContext, AssertionMethod, ContractAnnotation]
  - Fail.IfArgumentWhiteSpace(
      argumentValue: string [CanBeNull, AssertionCondition],
-     argumentName: string [NotNull, NotNull]
+     argumentName: string? [Nullable, CallerArgumentExpression, Optional]
    ) : void [AssertionMethod, ContractAnnotation]
  - Fail.IfCollectionContains<T>(
      collection: IEnumerable<T> [CanBeNull, AssertionCondition],
diff --git a/Contracts/Synergy.Contracts.Test/Failures/Doubles/Contractor.cs b/Contracts/Synergy.Contracts.Test/Failures/Doubles/Contractor.cs
index a6b8643..5db8a0b 100644
--- a/Contracts/Synergy.Contracts.Test/Failures/Doubles/Contractor.cs
+++ b/Contracts/Synergy.Contracts.Test/Failures/Doubles/Contractor.cs
@@ -19,10 +19,10 @@ public static Contractor CreateCompany([NotNull] string name)
         }
 
         [NotNull, Pure]
-        public static Contractor CreatePerson([NotNull] string firstName, [NotNull] string lastName)
+        public static Contractor CreatePerson(string firstName, string lastName)
         {
             Fail.IfArgumentEmpty(firstName);
-            Fail.IfArgumentWhiteSpace(lastName, nameof(lastName));
+            Fail.IfArgumentWhiteSpace(lastName);
 
             return new Contractor()
             {
diff --git a/Contracts/Synergy.Contracts.Test/Failures/FailStringTest.cs b/Contracts/Synergy.Contracts.Test/Failures/FailStringTest.cs
index 7df9726..f5ae40b 100644
Binary files a/Contracts/Synergy.Contracts.Test/Failures/FailStringTest.cs and b/Contracts/Synergy.Contracts.Test/Failures/FailStringTest.cs differ
diff --git a/Contracts/Synergy.Contracts/Failures/FailString.cs b/Contracts/Synergy.Contracts/Failures/FailString.cs
index 3a86a6e..6e5fdbb 100644
--- a/Contracts/Synergy.Contracts/Failures/FailString.cs
+++ b/Contracts/Synergy.Contracts/Failures/FailString.cs
@@ -85,7 +85,13 @@ public static void IfEmpty(
         [ContractAnnotation("argumentValue: null => halt")]
         public static void IfArgumentWhiteSpace(
             [CanBeNull, AssertionCondition(AssertionConditionType.IS_NOT_NULL)] string argumentValue,
-            [NotNull] [System.Diagnostics.CodeAnalysis.NotNull] string argumentName)
+#if NET6_0_OR_GREATER
+            [System.Runtime.CompilerServices.CallerArgumentExpression("argumentValue")]
+            string? argumentName = null
+#else
+            string argumentName
+#endif
+            )
         {
             Fail.RequiresArgumentName(argumentName);
             Fail.IfArgumentNull(argumentValue, argumentName);