diff --git a/java-collections-conversions/src/main/java/com/baeldung/convertToMap/ConvertToMap.java b/java-collections-conversions/src/main/java/com/baeldung/convertToMap/ConvertToMap.java
index 3c14dfdba6..e33d9ee212 100644
--- a/java-collections-conversions/src/main/java/com/baeldung/convertToMap/ConvertToMap.java
+++ b/java-collections-conversions/src/main/java/com/baeldung/convertToMap/ConvertToMap.java
@@ -15,8 +15,7 @@ public class ConvertToMap {
     }
 
     public Map<Integer, Book> listToMapWithDupKey(List<Book> books) {
-        return books.stream().collect(Collectors.toMap(Book::getReleaseYear, Function.identity(),
-                (o1, o2) -> o1));
+        return books.stream().collect(Collectors.toMap(Book::getReleaseYear, Function.identity(), (existing, replacement) -> existing));
     }
 
     public Map<Integer, Book> listToConcurrentMap(List<Book> books) {
diff --git a/java-collections-conversions/src/test/java/com/baeldung/convertToMap/ConvertToMapUnitTest.java b/java-collections-conversions/src/test/java/com/baeldung/convertToMap/ConvertToMapUnitTest.java
index d11221bbf7..d6eab461d7 100644
--- a/java-collections-conversions/src/test/java/com/baeldung/convertToMap/ConvertToMapUnitTest.java
+++ b/java-collections-conversions/src/test/java/com/baeldung/convertToMap/ConvertToMapUnitTest.java
@@ -2,6 +2,7 @@ package com.baeldung.convertToMap;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 
 import static org.junit.Assert.*;
@@ -34,8 +35,10 @@ public class ConvertToMapUnitTest {
     }
 
     @Test
-    public void whenMapHasDuplicateKey_with_merge_function() {
-        assertTrue(convertToMap.listToMapWithDupKey(bookList).size() == 2);
+    public void whenMapHasDuplicateKeyThenMergeFunctionHandlesCollision() {
+        Map<Integer, Book> booksByYear = convertToMap.listToMapWithDupKey(bookList);
+        assertEquals(2, booksByYear.size());
+        assertEquals("0395489318", booksByYear.get(1954).getIsbn());
     }
 
     @Test