diff --git a/X10D.Tests/src/Linq/EnumerableTests.cs b/X10D.Tests/src/Linq/EnumerableTests.cs
index e211309..e77d4f9 100644
--- a/X10D.Tests/src/Linq/EnumerableTests.cs
+++ b/X10D.Tests/src/Linq/EnumerableTests.cs
@@ -34,7 +34,7 @@ public class EnumerableTests
     public void ConcatOne_ShouldThrowArgumentNullException_GivenNullSource()
     {
         IEnumerable<string>? source = null;
-        Assert.ThrowsException<ArgumentNullException>(() => source!.ConcatOne("Foobar"));
+        Assert.ThrowsException<ArgumentNullException>(() => source!.ConcatOne("Foobar").ToArray());
     }
 
     [TestMethod]