diff --git a/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v1/dynamodb/DynamodbAttributeValueTransformerTest.java b/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v1/dynamodb/DynamodbAttributeValueTransformerTest.java
index 4c982ac5..14534fae 100644
--- a/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v1/dynamodb/DynamodbAttributeValueTransformerTest.java
+++ b/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v1/dynamodb/DynamodbAttributeValueTransformerTest.java
@@ -179,6 +179,7 @@ public void testToAttributeValueV1_L() {
         com.amazonaws.services.dynamodbv2.model.AttributeValue convertedAttributeValueL =
                 DynamodbAttributeValueTransformer.toAttributeValueV1(attributeValueL_event);
         Assertions.assertEquals(attributeValueL_v1, convertedAttributeValueL);
+        Assertions.assertEquals("ArrayList", convertedAttributeValueL.getL().getClass().getSimpleName(), "List is mutable");
     }
 
     @Test
@@ -262,12 +263,14 @@ public void testToAttributeValueV1_DoesNotThrowWhenEmpty_BS() {
 
     @Test
     public void testToAttributeValueV1_DoesNotThrowWhenEmpty_L() {
-        Assertions.assertDoesNotThrow(() ->
-                DynamodbAttributeValueTransformer.toAttributeValueV1(new AttributeValue().withL())
-        );
-        Assertions.assertDoesNotThrow(() ->
-                DynamodbAttributeValueTransformer.toAttributeValueV1(new AttributeValue().withL(Collections.emptyList()))
-        );
+        Assertions.assertDoesNotThrow(() -> {
+            com.amazonaws.services.dynamodbv2.model.AttributeValue attributeValue = DynamodbAttributeValueTransformer.toAttributeValueV1(new AttributeValue().withL());
+            Assertions.assertEquals("ArrayList", attributeValue.getL().getClass().getSimpleName(), "List is mutable");
+        });
+        Assertions.assertDoesNotThrow(() -> {
+            com.amazonaws.services.dynamodbv2.model.AttributeValue attributeValue = DynamodbAttributeValueTransformer.toAttributeValueV1(new AttributeValue().withL(Collections.emptyList()));
+            Assertions.assertEquals("ArrayList", attributeValue.getL().getClass().getSimpleName(), "List is mutable");
+        });
     }
 
     @Test
diff --git a/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v2/dynamodb/DynamodbAttributeValueTransformerTest.java b/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v2/dynamodb/DynamodbAttributeValueTransformerTest.java
index 10bab4f6..1c7f05f7 100644
--- a/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v2/dynamodb/DynamodbAttributeValueTransformerTest.java
+++ b/aws-lambda-java-events-sdk-transformer/src/test/java/com/amazonaws/services/lambda/runtime/events/transformers/v2/dynamodb/DynamodbAttributeValueTransformerTest.java
@@ -183,6 +183,7 @@ public void testToAttributeValueV2_L() {
         software.amazon.awssdk.services.dynamodb.model.AttributeValue convertedAttributeValueL =
                 DynamodbAttributeValueTransformer.toAttributeValueV2(attributeValueL_event);
         Assertions.assertEquals(attributeValueL_v2, convertedAttributeValueL);
+        Assertions.assertEquals("UnmodifiableRandomAccessList", convertedAttributeValueL.l().getClass().getSimpleName(), "List is immutable");
     }
 
     @Test
@@ -266,12 +267,14 @@ public void testToAttributeValueV2_DoesNotThrowWhenEmpty_BS() {
 
     @Test
     public void testToAttributeValueV2_DoesNotThrowWhenEmpty_L() {
-        Assertions.assertDoesNotThrow(() ->
-                DynamodbAttributeValueTransformer.toAttributeValueV2(new AttributeValue().withL())
-        );
-        Assertions.assertDoesNotThrow(() ->
-                DynamodbAttributeValueTransformer.toAttributeValueV2(new AttributeValue().withL(Collections.emptyList()))
-        );
+        Assertions.assertDoesNotThrow(() -> {
+            software.amazon.awssdk.services.dynamodb.model.AttributeValue attributeValue = DynamodbAttributeValueTransformer.toAttributeValueV2(new AttributeValue().withL());
+            Assertions.assertEquals("UnmodifiableRandomAccessList", attributeValue.l().getClass().getSimpleName(), "List is immutable");
+        });
+        Assertions.assertDoesNotThrow(() -> {
+            software.amazon.awssdk.services.dynamodb.model.AttributeValue attributeValue = DynamodbAttributeValueTransformer.toAttributeValueV2(new AttributeValue().withL(Collections.emptyList()));
+            Assertions.assertEquals("UnmodifiableRandomAccessList", attributeValue.l().getClass().getSimpleName(), "List is immutable");
+        });
     }
 
     @Test