diff -u b/core/modules/config/src/Tests/ConfigSchemaTest.php b/core/modules/config/src/Tests/ConfigSchemaTest.php
--- b/core/modules/config/src/Tests/ConfigSchemaTest.php
+++ b/core/modules/config/src/Tests/ConfigSchemaTest.php
@@ -300,6 +300,12 @@
     $this->assertTrue(isset($list['front']) && isset($list['403']) && isset($list['404']), 'Got a list with the right properties for site page data.');
     $this->assertEqual($list['front']->getValue(), 'user/login', 'Got the right value for page.front data from the list.');
 
+    // And test some TypedConfigInterface methods.
+    $properties = $list;
+    $this->assertTrue(count($properties) == 3 && $properties['front'] == $list['front'], 'Got the right properties for site page.');
+    $values = $meta->get('page')->toArray();
+    $this->assertTrue(count($values) == 3 && $values['front'] == 'user/login', 'Got the right property values for site page.');
+
     // Now let's try something more complex, with nested objects.
     $wrapper = \Drupal::service('config.typed')->get('image.style.large');
     $effects = $wrapper->get('effects');