diff --git a/core/lib/Drupal/Core/Entity/Field/FieldDefinition.php b/core/lib/Drupal/Core/Entity/Field/FieldDefinition.php
index c8e2d9f..dd9ef34 100644
--- a/core/lib/Drupal/Core/Entity/Field/FieldDefinition.php
+++ b/core/lib/Drupal/Core/Entity/Field/FieldDefinition.php
@@ -281,8 +281,9 @@ public static function createFromOldStyleDefinition(array $definition) {
     $list_definition = $definition;
     unset($list_definition['type']);
 
-    // Constraints and settings apply to the list item.
+    // Constraints, class and settings apply to the list item.
     unset($list_definition['constraints']);
+    unset($list_definition['class']);
     unset($list_definition['settings']);
 
     $field_definition = new FieldDefinition($list_definition);
diff --git a/core/lib/Drupal/Core/TypedData/DataDefinition.php b/core/lib/Drupal/Core/TypedData/DataDefinition.php
index 7e396de..90763fc 100644
--- a/core/lib/Drupal/Core/TypedData/DataDefinition.php
+++ b/core/lib/Drupal/Core/TypedData/DataDefinition.php
@@ -327,10 +327,11 @@ public static function createFromOldStyleDefinition(array $definition) {
     unset($definition['list']);
 
     $list_definition = $definition;
-    $list_definition['type'] = 'list';
+    unset($list_definition['type']);
 
-    // Constraints and settings apply to the list item.
+    // Constraints, class and settings apply to the list item.
     unset($list_definition['constraints']);
+    unset($list_definition['class']);
     unset($list_definition['settings']);
 
     $list_definition = new ListDefinition($list_definition);