diff --git a/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php b/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php
index b6a384f..02f1d7e 100644
--- a/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php
+++ b/core/lib/Drupal/Core/Config/Schema/ListElementInterface.php
@@ -38,7 +38,7 @@ public function isEmpty();
   public function getElements();
 
   /**
-   * Gets a element object.
+   * Gets a contained typed configuration element.
    *
    * @param $property_name
    *   The name of the property to get; e.g., 'title' or 'name'. Nested
diff --git a/core/modules/config_translation/tests/src/ConfigMapperManagerTest.php b/core/modules/config_translation/tests/src/ConfigMapperManagerTest.php
index 86a4719..d7c47cb 100644
--- a/core/modules/config_translation/tests/src/ConfigMapperManagerTest.php
+++ b/core/modules/config_translation/tests/src/ConfigMapperManagerTest.php
@@ -170,7 +170,12 @@ protected function getElement(array $definition) {
    *   A nested schema element, containing the passed-in elements.
    */
   protected function getNestedElement(array $elements) {
-    $nested_element = $this->getMock('Drupal\Core\Config\Schema\ListElementInterface');
+    // ConfigMapperManager::findTranslatable() checks for the abstract class
+    // \Drupal\Core\Config\Schema\ArrayElement, but mocking that directly does
+    // not work.
+    $nested_element = $this->getMockBuilder('Drupal\Core\Config\Schema\Mapping')
+      ->disableOriginalConstructor()
+      ->getMock();
     $nested_element->expects($this->once())
       ->method('getIterator')
       ->will($this->returnValue(new \ArrayIterator($elements)));