diff --git a/core-java-modules/core-java-10/src/test/java/com/baeldung/java10/list/CopyListServiceUnitTest.java b/core-java-modules/core-java-10/src/test/java/com/baeldung/java10/list/CopyListServiceUnitTest.java
index f529e219a6..0b70516146 100644
--- a/core-java-modules/core-java-10/src/test/java/com/baeldung/java10/list/CopyListServiceUnitTest.java
+++ b/core-java-modules/core-java-10/src/test/java/com/baeldung/java10/list/CopyListServiceUnitTest.java
@@ -10,5 +10,6 @@ public class CopyListServiceUnitTest {
     @Test(expected = UnsupportedOperationException.class)
     public void whenModifyCopyOfList_thenThrowsException() {
         List<Integer> copyList = List.copyOf(Arrays.asList(1, 2, 3, 4));
+        copyList.add(4);
     }
 }